CHAPTER 1 — History of Diving 1-1
This chapter provides a general history of the development of military
This chapter outlines the hard work and dedication of a number of individ-
uals who were pioneers in the development of diving technology. As with any
endeavor, it is important to build the on discoveries of our predecessors and not
repeat mistakes of the past.
Role of the U.S. Navy.
The U.S. Navy is a leader in the development of modern
diving and underwater operations. The general requirements of national defense
and the specific requirements of underwater reconnaissance, demolition, ordnance
disposal, construction, ship maintenance, search, rescue and salvage operations
repeatedly give impetus to training and development. Navy diving is no longer
limited to tactical combat operations, wartime salvage, and submarine sinkings.
Fleet diving has become increasingly important and diversified since World War
II. A major part of the diving mission is inspecting and repairing naval vessels to
minimize downtime and the need for dry-docking. Other aspects of fleet diving
include recovering practice and research torpedoes, installing and repairing under-
water electronic arrays, underwater construction, and locating and recovering
SURFACE-SUPPLIED AIR DIVING
The origins of diving are firmly rooted in man’s need and desire to engage in mari-
time commerce, to conduct salvage and military operations, and to expand the
frontiers of knowledge through exploration, research, and development.
Diving, as a profession, can be traced back more than 5,000 years. Early divers
confined their efforts to waters less than 100 feet deep, performing salvage work
and harvesting food, sponges, coral, and mother-of-pearl. A Greek historian,
Herodotus, recorded the story of a diver named Scyllis, who was employed by the
Persian King Xerxes to recover sunken treasure in the fifth century B.C.
From the earliest times, divers were active in military operations. Their missions
included cutting anchor cables to set enemy ships adrift, boring or punching holes
in the bottoms of ships, and building harbor defenses at home while attempting to
destroy those of the enemy abroad. Alexander the Great sent divers down to
remove obstacles in the harbor of the city of Tyre, in what is now Lebanon, which
he had taken under siege in 332 B.C.
Other early divers developed an active salvage industry centered around the major
shipping ports of the eastern Mediterranean. By the first century B.C., operations
1-2 U.S. Navy Diving Manual—Volume 1
in one area had become so well organized that a payment scale for salvage work
was established by law, acknowledging the fact that effort and risk increased with
depth. In 24 feet of water, the divers could claim a one-half share of all goods
recovered. In 12 feet of water, they were allowed a one-third share, and in 3 feet,
only a one-tenth share.
The most obvious and crucial step to broadening a diver’s capa-
bilities was providing an air supply that would permit him to stay underwater.
Hollow reeds or tubes extending to the surface allowed a diver to remain
submerged for an extended period, but he could accomplish little in the way of
useful work. Breathing tubes were employed in military operations, permitting an
undetected approach to an enemy stronghold (Figure 1-1).
At first glance, it seemed logical that a longer breathing tube was the only require-
ment for extending a diver’s range. In fact, a number of early designs used leather
hoods with long flexible tubes supported at the surface by floats. There is no
record, however, that any of these devices were actually constructed or tested. The
result may well have been the drowning of the diver. At a depth of 3 feet, it is
nearly impossible to breathe through a tube using only the body’s natural respira-
tory ability, as the weight of the water exerts a total force of almost 200 pounds on
the diver’s chest. This force increases steadily with depth and is one of the most
important factors in diving. Successful diving operations require that the pressure
be overcome or eliminated. Throughout history, imaginative devices were
designed to overcome this problem, many by some of the greatest minds of the
time. At first, the problem of pressure underwater was not fully understood and the
designs were impractical.
Early Impractical Breathing Device.
This 1511 design shows the diver’s head encased
in a leather bag with a breathing tube extending to
Assyrian Frieze (900 B.C.).
CHAPTER 1 — History of Diving 1-3
An entire series of designs was based on the idea of a breathing
bag carried by the diver. An Assyrian frieze of the ninth century B.C. shows what
appear to be divers using inflated animal skins as air tanks. However, these men
were probably swimmers using skins for flotation. It would be impossible to
submerge while holding such an accessory (Figure 1-2).
A workable diving system may have made a brief appearance in the later Middle
Ages. In 1240, Roger Bacon made reference to “instruments whereby men can
walk on sea or river beds without danger to themselves.”
Between 1500 and 1800 the diving bell was developed, enabling
divers to remain underwater for hours rather than minutes. The diving bell is a
bell-shaped apparatus with the bottom open to the sea.
The first diving bells were large, strong tubs weighted to sink in a vertical posi-
tion, trapping enough air to permit a diver to breathe for several hours. Later
diving bells were suspended by a cable from the surface. They had no significant
underwater maneuverability beyond that provided by moving the support ship.
The diver could remain in the bell if positioned directly over his work, or could
venture outside for short periods of time by holding his breath.
The first reference to an actual practical diving bell was made in 1531. For several
hundred years thereafter, rudimentary but effective bells were used with regularity.
In the 1680s, a Massachusetts-born adventurer named William Phipps modified
the diving bell technique by supplying his divers with air from a series of
weighted, inverted buckets as they attempted to recover treasure valued at
In 1690, the English astronomer Edmund Halley developed a diving bell in which
the atmosphere was replenished by sending weighted barrels of air down from the
surface (Figure 1-3). In an early demonstration of his system, he and four compan-
ions remained at 60 feet in the Thames River for almost 1½ hours. Nearly 26 years
later, Halley spent more than 4 hours at 66 feet using an improved version of his
Diving Dress Designs.
With an increasing number of military and civilian wrecks
littering the shores of Great Britain each year, there was strong incentive to
develop a diving dress that would increase the efficiency of salvage operations.
Lethbridge’s Diving Dress.
In 1715, Englishman John Lethbridge developed a
one-man, completely enclosed diving dress (Figure 1-4). The Lethbridge equip-
ment was a reinforced, leather-covered barrel of air, equipped with a glass
porthole for viewing and two arm holes with watertight sleeves. Wearing this gear,
the occupant could accomplish useful work. This apparatus was lowered from a
ship and maneuvered in the same manner as a diving bell.
Lethbridge was quite successful with his invention and participated in salvaging a
number of European wrecks. In a letter to the editor of a popular magazine in
1749, the inventor noted that his normal operating depth was 10 fathoms (60 feet),
1-4 U.S. Navy Diving Manual—Volume 1
with about 12 fathoms the maximum, and that he could remain underwater for 34
Several designs similar to Lethbridge’s were used in succeeding years. However,
all had the same basic limitation as the diving bell—the diver had little freedom
because there was no practical way to continually supply him with air. A true tech-
nological breakthrough occurred at the turn of the 19th century when a hand-
operated pump capable of delivering air under pressure was developed.
Deane’s Patented Diving Dress.
Several men produced a successful apparatus at
the same time. In 1823, two salvage operators, John and Charles Deane, patented
the basic design for a smoke apparatus that permitted firemen to move about in
burning buildings. By 1828, the apparatus evolved into Deane’s Patent Diving
Dress, consisting of a heavy suit for protection from the cold, a helmet with
viewing ports, and hose connections for delivering surface-supplied air. The
helmet rested on the diver’s shoulders, held in place by its own weight and straps
to a waist belt. Exhausted or surplus air passed out from under the edge of the
helmet and posed no problem as long as the diver was upright. If he fell, however,
the helmet could quickly fill with water. In 1836, the Deanes issued a diver’s
manual, perhaps the first ever produced.
Siebe’s Improved Diving Dress.
Credit for developing the first practical diving
dress has been given to Augustus Siebe. Siebe’s initial contribution to diving was a
modification of the Deane outfit. Siebe sealed the helmet to the dress at the collar
by using a short, waist-length waterproof suit and added an exhaust valve to the
system (Figure 1-5). Known as Siebe’s Improved Diving Dress, this apparatus is
the direct ancestor of the MK V standard deep-sea diving dress.
Engraving of Halley’s
Lethbridge’s Diving Suit.
CHAPTER 1 — History of Diving 1-5
Salvage of the HMS
By 1840, sev-
eral types of diving dress were being used in actual
diving operations. At that time, a unit of the British
Royal Engineers was engaged in removing the re-
mains of the sunken warship, HMS Royal George.
The warship was fouling a major fleet anchorage
just outside Portsmouth, England. Colonel William
Pasley, the officer in charge, decided that his oper-
ation was an ideal opportunity to formally test and
evaluate the various types of apparatus. Wary of
the Deane apparatus because of the possibility of
helmet flooding, he formally recommended that
the Siebe dress be adopted for future operations.
When Pasley’s project was completed, an official
government historian noted that “of the seasoned
divers, not a man escaped the repeated attacks of
rheumatism and cold.” The divers had been
working for 6 or 7 hours a day, much of it spent at
depths of 60 to 70 feet. Pasley and his men did not
realize the implications of the observation. What
appeared to be rheumatism was instead a symptom of a far more serious physio-
logical problem that, within a few years, was to become of great importance to the
At the same time that a practical diving dress was being perfected,
inventors were working to improve the diving bell by increasing its size and
adding high-capacity air pumps that could deliver enough pressure to keep water
entirely out of the bell’s interior. The improved pumps soon led to the construction
of chambers large enough to permit several men to engage in dry work on the
bottom. This was particularly advantageous for projects such as excavating bridge
footings or constructing tunnel sections where long periods of work were required.
These dry chambers were known as caissons, a French word meaning “big boxes”
Enclosed Diving Dress and
French Caisson. This
caisson could be floated over the
work site and lowered to the bottom
by flooding the side tanks.
1-6 U.S. Navy Diving Manual—Volume 1
Caissons were designed to provide ready access from the surface. By using an air
lock, the pressure inside could be maintained while men or materials could be
passed in and out. The caisson was a major step in engineering technology and its
use grew quickly.
Caisson Disease (Decompression Sickness).
With the increasing use of cais-
sons, a new and unexplained malady began to affect the caisson workers. Upon
returning to the surface at the end of a shift, the divers frequently would be struck
by dizzy spells, breathing difficulties, or sharp pains in the joints or abdomen. The
sufferer usually recovered, but might never be completely free of some of the
symptoms. Caisson workers often noted that they felt better working on the job,
but wrongly attributed this to being more rested at the beginning of a shift.
As caisson work extended to larger projects and to greater operating pressures, the
physiological problems increased in number and severity. Fatalities occurred with
alarming frequency. The malady was called, logically enough, caisson disease.
However, workers on the Brooklyn Bridge project in New York gave the sickness
a more descriptive name that has remained—the “bends.”
Today the bends is the most well-known danger of diving. Although men had been
diving for thousands of years, few men had spent much time working under great
atmospheric pressure until the time of the caisson. Individuals such as Pasley, who
had experienced some aspect of the disease, were simply not prepared to look for
anything more involved than indigestion, rheumatism, or arthritis.
Cause of Decompression Sickness.
The actual cause of caisson disease was first
clinically described in 1878 by a French physiologist, Paul Bert. In studying the
effect of pressure on human physiology, Bert determined that breathing air under
pressure forced quantities of nitrogen into solution in the blood and tissues of the
body. As long as the pressure remained, the gas was held in solution. When the
pressure was quickly released, as it was when a worker left the caisson, the
nitrogen returned to a gaseous state too rapidly to pass out of the body in a natural
manner. Gas bubbles formed throughout the body, causing the wide range of
symptoms associated with the disease. Paralysis or death could occur if the flow of
blood to a vital organ was blocked by the bubbles.
Prevention and Treatment of Decompression Sickness.
Bert recommended that
caisson workers gradually decompress and divers return to the surface slowly. His
studies led to an immediate improvement for the caisson workers when they
discovered their pain could be relieved by returning to the pressure of the caisson
as soon as the symptom appeared.
Within a few years, specially designed recompression chambers were being placed
at job sites to provide a more controlled situation for handling the bends. The pres-
sure in the chambers could be increased or decreased as needed for an individual
worker. One of the first successful uses of a recompression chamber was in 1879
during the construction of a subway tunnel under the Hudson River between New
CHAPTER 1 — History of Diving 1-7
York and New Jersey. The recompression chamber markedly reduced the number
of serious cases and fatalities caused by the bends.
Bert’s recommendation that divers ascend gradually and steadily was not a
complete success, however; some divers continued to suffer from the bends. The
general thought at the time was that divers had reached the practical limits of the
art and that 120 feet was about as deep as anyone could work. This was because of
the repeated incidence of the bends and diver inefficiency beyond that depth.
Occasionally, divers would lose consciousness while working at 120 feet.
J.S. Haldane, an English physiologist, conducted experi-
ments with Royal Navy divers from 1905 to 1907. He determined that part of the
problem was due to the divers not adequately ventilating their helmets, causing
high levels of carbon dioxide to accumulate. To solve the problem, he established
a standard supply rate of flow (1.5 cubic feet of air per minute, measured at the
pressure of the diver). Pumps capable of maintaining the flow and ventilating the
helmet on a continuous basis were used.
Haldane also composed a set of diving tables that established a method of decom-
pression in stages. Though restudied and improved over the years, these tables
remain the basis of the accepted method for bringing a diver to the surface.
As a result of Haldane’s studies, the practical operating depth for air divers was
extended to slightly more than 200 feet. The limit was not imposed by physiolog-
ical factors, but by the capabilities of the hand-pumps available to provide the air
Divers soon were moving into
deeper water and another unexplained malady
began to appear. The diver would appear intoxi-
cated, sometimes feeling euphoric and frequently
losing judgment to the point of forgetting the dive’s
purpose. In the 1930s this “rapture of the deep” was
linked to nitrogen in the air breathed under higher
pressures. Known as nitrogen narcosis, this condi-
tion occurred because nitrogen has anesthetic
properties that become progressively more severe
with increasing air pressure. To avoid the problem,
special breathing mixtures such as helium-oxygen
were developed for deep diving (see section 1-4,
Armored Diving Suits.
Numerous inventors, many
with little or no underwater experience, worked to
create an armored diving suit that would free the
diver from pressure problems (Figure 1-7). In an ar-
mored suit, the diver could breathe air at normal
atmospheric pressure and descend to great depths
without any ill effects. The barrel diving suit, de-
1-8 U.S. Navy Diving Manual—Volume 1
signed by John Lethbridge in 1715, had been an armored suit in essence, but one
with a limited operating depth.
The utility of most armored suits was questionable. They were too clumsy for the
diver to be able to accomplish much work and too complicated to provide protec-
tion from extreme pressure. The maximum anticipated depth of the various suits
developed in the 1930s was 700 feet, but was never reached in actual diving. More
recent pursuits in the area of armored suits, now called one-atmosphere diving
suits, have demonstrated their capability for specialized underwater tasks to 2,000
feet of saltwater (fsw).
MK V Deep-Sea Diving Dress.
By 1905, the Bureau of Construction and Repair
had designed the MK V Diving Helmet which seemed to address many of the
problems encountered in diving. This deep-sea outfit was designed for extensive,
rugged diving work and provided the diver maximum physical protection and
The 1905 MK V Diving Helmet had an elbow inlet with a safety valve that
allowed air to enter the helmet, but not to escape back up the umbilical if the air
supply were interrupted. Air was expelled from the helmet through an exhaust
valve on the right side, below the port. The exhaust valve was vented toward the
rear of the helmet to prevent escaping bubbles from interfering with the diver’s
field of vision.
By 1916, several improvements had been made to the helmet, including a rudi-
mentary communications system via a telephone cable and a regulating valve
operated by an interior push button. The regulating valve allowed some control of
the atmospheric pressure. A supplementary relief valve, known as the spitcock,
was added to the left side of the helmet. A safety catch was also incorporated to
keep the helmet attached to the breast plate. The exhaust valve and the communi-
cations system were improved by 1927, and the weight of the helmet was
decreased to be more comfortable for the diver.
After 1927, the MK V changed very little. It remained basically the same helmet
used in salvage operations of the USS S-51 and USS S-4 in the mid-1920s. With
its associated deep-sea dress and umbilical, the MK V was used for all submarine
rescue and salvage work undertaken in peacetime and practically all salvage work
undertaken during World War II. The MK V Diving Helmet was the standard U.S.
Navy diving equipment until succeeded by the MK 12 Surface-Supplied Diving
System (SSDS) in February 1980 (see Figure 1-8). The MK 12 was replaced by
the MK 21 in December 1993.
The diving equipment developed by Charles and John Deane, Augustus Siebe, and
other inventors gave man the ability to remain and work underwater for extended
periods, but movement was greatly limited by the requirement for surface-
supplied air. Inventors searched for methods to increase the diver’s movement
CHAPTER 1 — History of Diving 1-9
without increasing the hazards. The best solution was to provide the diver with a
portable, self-contained air supply. For many years the self-contained underwater
breathing apparatus (scuba) was only a theoretical possibility. Early attempts to
supply self-contained compressed air to divers were not successful due to the limi-
tations of air pumps and containers to compress and store air at sufficiently high
pressure. Scuba development took place gradually, however, evolving into three
Open-circuit scuba (where the exhaust is vented directly to the surrounding
Closed-circuit scuba (where the oxygen is filtered and recirculated), and
Semiclosed-circuit scuba (which combines features of the open- and closed-
In the open-circuit apparatus, air is inhaled from a supply
cylinder and the exhaust is vented directly to the surrounding water.
Rouquayrol’s Demand Regulator.
The first and highly necessary component of
an open-circuit apparatus was a demand regulator. Designed early in 1866 and
patented by Benoist Rouquayrol, the regulator adjusted the flow of air from the
tank to meet the diver’s breathing and pressure requirements. However, because
cylinders strong enough to contain air at high pressure could not be built at the
time, Rouquayrol adapted his regulator to surface-supplied diving equipment and
the technology turned toward closed-circuit designs. The application of
Rouquayrol’s concept of a demand regulator to a successful open-circuit scuba
was to wait more than 60 years.
LePrieur’s Open-Circuit Scuba Design.
The thread of open-circuit development
was picked up in 1933. Commander LePrieur, a French naval officer, constructed
an open-circuit scuba using a tank of compressed air. However, LePrieur did not
include a demand regulator in his design and, the diver’s main effort was diverted
MK 12 and MK V.
1-10 U.S. Navy Diving Manual—Volume 1
to the constant manual control of his air supply. The lack of a demand regulator,
coupled with extremely short endurance, severely limited the practical use of
Cousteau and Gagnan’s Aqua-Lung.
At the same time that actual combat opera-
tions were being carried out with closed-circuit apparatus, two Frenchmen
achieved a significant breakthrough in open-circuit scuba design. Working in a
small Mediterranean village, under the difficult and restrictive conditions of
German-occupied France, Jacques-Yves Cousteau and Emile Gagnan combined an
improved demand regulator with high-pressure air tanks to create the first truly
efficient and safe open-circuit scuba, known as the Aqua-Lung. Cousteau and his
companions brought the Aqua-Lung to a high state of development as they
explored and photographed wrecks, developing new diving techniques and testing
The Aqua-Lung was the culmination of hundreds of years of progress, blending
the work of Rouquayol, LePrieur, and Fleuss, a pioneer in closed-circuit scuba
development. Cousteau used his gear successfully to 180 fsw without significant
difficulty and with the end of the war the Aqua-Lung quickly became a commer-
cial success. Today the Aqua-Lung is the most widely used diving equipment,
opening the underwater world to anyone with suitable training and the funda-
mental physical abilities.
Impact of Scuba on Diving.
The underwater freedom brought about by the devel-
opment of scuba led to a rapid growth of interest in diving. Sport diving has
become very popular, but science and commerce have also benefited. Biologists,
geologists and archaeologists have all gone underwater, seeking new clues to the
origins and behavior of the earth, man and civilization as a whole. An entire
industry has grown around commercial diving, with the major portion of activity
in offshore petroleum production.
After World War II, the art and science of diving progressed rapidly, with
emphasis placed on improving existing diving techniques, creating new methods,
and developing the equipment required to serve these methods. A complete gener-
ation of new and sophisticated equipment took form, with substantial
improvements being made in both open and closed-circuit apparatus. However,
the most significant aspect of this technological expansion has been the closely
linked development of saturation diving techniques and deep diving systems.
The basic closed-circuit system, or oxygen rebreather, uses
a cylinder of 100 percent oxygen that supplies a breathing bag. The oxygen used
by the diver is recirculated in the apparatus, passing through a chemical filter that
removes carbon dioxide. Oxygen is added from the tank to replace that consumed
in breathing. For special warfare operations, the closed-circuit system has a major
advantage over the open-circuit type: it does not produce a telltale trail of bubbles
on the surface.
Fleuss’ Closed-Circuit Scuba.
Henry A. Fleuss developed the first commercially
practical closed-circuit scuba between 1876 and 1878 (Figure 1-9). The Fleuss
CHAPTER 1 — History of Diving 1-11
device consisted of a watertight rubber face mask and a breathing bag connected
to a copper tank of 100 percent oxygen charged to 450 psi. By using oxygen
instead of compressed air as the breathing medium, Fleuss eliminated the need for
high-strength tanks. In early models of this apparatus, the diver controlled the
makeup feed of fresh oxygen with a hand valve.
Fleuss successfully tested his apparatus in 1879. In the
first test, he remained in a tank of water for about an
hour. In the second test, he walked along a creek bed at
a depth of 18 feet. During the second test, Fleuss turned
off his oxygen feed to see what would happen. He was
soon unconscious, and suffered gas embolism as his
tenders pulled him to the surface. A few weeks after his
recovery, Fleuss made arrangements to put his recircu-
lating design into commercial production.
In 1880, the Fleuss scuba figured prominently in a
highly publicized achievement by an English diver,
Alexander Lambert. A tunnel under the Severn River
flooded and Lambert, wearing a Fleuss apparatus,
walked 1,000 feet along the tunnel, in complete dark-
ness, to close several crucial valves.
Modern Closed-Circuit Systems.
As development of
the closed-circuit design continued, the Fleuss equip-
ment was improved by adding a demand regulator and
tanks capable of holding oxygen at more than 2,000
psi. By World War I, the Fleuss scuba (with modifica-
tions) was the basis for submarine escape equipment
used in the Royal Navy. In World War II, closed-circuit
units were widely used for combat diving operations
(see paragraph 1-3.5.2).
Some modern closed-circuit systems employ a mixed gas for breathing and elec-
tronically senses and controls oxygen concentration. This type of apparatus retains
the bubble-free characteristics of 100-percent oxygen recirculators while signifi-
cantly improving depth capability.
Hazards of Using Oxygen in Scuba.
Fleuss had been unaware of the serious
problem of oxygen toxicity caused by breathing 100 percent oxygen under pres-
sure. Oxygen toxicity apparently was not encountered when he used his apparatus
in early shallow water experiments. The danger of oxygen poisoning had actually
been discovered prior to 1878 by Paul Bert, the physiologist who first proposed
controlled decompression as a way to avoid the bends. In laboratory experiments
with animals, Bert demonstrated that breathing oxygen under pressure could lead
to convulsions and death (central nervous system oxygen toxicity).
1-12 U.S. Navy Diving Manual—Volume 1
In 1899, J. Lorrain Smith found that breathing oxygen over prolonged periods of
time, even at pressures not sufficient to cause convulsions, could lead to pulmo-
nary oxygen toxicity, a serious lung irritation. The results of these experiments,
however, were not widely publicized. For many years, working divers were
unaware of the dangers of oxygen poisoning.
The true seriousness of the problem was not apparent until large numbers of
combat swimmers were being trained in the early years of World War II. After a
number of oxygen toxicity accidents, the British established an operational depth
limit of 33 fsw. Additional research on oxygen toxicity continued in the U.S. Navy
after the war and resulted in the setting of a normal working limit of 25 fsw for 75
minutes for the Emerson oxygen rebreather. A maximum emergency depth/time
limit of 40 fsw for 10 minutes was also allowed.
These limits eventually proved operationally restrictive, and prompted the Navy
Experimental Diving Unit to reexamine the entire problem of oxygen toxicity in
the mid-1980s. As a result of this work, more liberal and flexible limits were
adopted for U.S. Navy use.
The semiclosed-circuit scuba combines features of
the open and closed-circuit systems. Using a mixture of gases for breathing, the
apparatus recycles the gas through a carbon dioxide removal canister and continu-
ally adds a small amount of oxygen-rich mixed gas to the system from a supply
cylinder. The supply gas flow is preset to satisfy the body’s oxygen demand; an
equal amount of the recirculating mixed-gas stream is continually exhausted to the
water. Because the quantity of makeup gas is constant regardless of depth, the
semiclosed-circuit scuba provides significantly greater endurance than open-
circuit systems in deep diving.
Lambertsen’s Mixed-Gas Rebreather.
In the late 1940s, Dr. C.J. Lambertsen
proposed that mixtures of nitrogen or helium with an elevated oxygen content be
used in scuba to expand the depth range beyond that allowed by 100-percent
oxygen rebreathers, while simultaneously minimizing the requirement for
In the early 1950s, Lambertsen introduced the FLATUS I, a semiclosed-circuit
scuba that continually added a small volume of mixed gas, rather than pure
oxygen, to a rebreathing circuit. The small volume of new gas provided the
oxygen necessary for metabolic consumption while exhaled carbon dioxide was
absorbed in an absorbent canister. Because inert gas, as well as oxygen, was added
to the rig, and because the inert gas was not consumed by the diver, a small
amount of gas mixture was continuously exhausted from the rig.
MK 6 UBA.
In 1964, after significant development work, the Navy adopted a
semiclosed-circuit, mixed-gas rebreather, the MK 6 UBA, for combat swimming
and EOD operations. Decompression procedures for both nitrogen-oxygen and
helium-oxygen mixtures were developed at the Navy Experimental Diving Unit.
The apparatus had a maximum depth capability of 200 fsw and a maximum endur-
ance of 3 hours depending on water temperature and diver activity. Because the
CHAPTER 1 — History of Diving 1-13
apparatus was based on a constant mass flow of mixed gas, the endurance was
independent of the diver’s depth.
In the late 1960s, work began on a new type of mixed-gas rebreather technology,
which was later used in the MK 15 and MK 16 UBAs. In this UBA, the oxygen
partial pressure was controlled at a constant value by an oxygen sensing and addi-
tion system. As the diver consumed oxygen, an oxygen sensor detected the fall in
oxygen partial pressure and signaled an oxygen valve to open, allowing a small
amount of pure oxygen to be admitted to the breathing circuit from a cylinder.
Oxygen addition was thus exactly matched to metabolic consumption. Exhaled
carbon dioxide was absorbed in an absorption canister. The system had the endur-
ance and completely closed-circuit characteristics of an oxygen rebreather without
the concerns and limitations associated with oxygen toxicity.
Beginning in 1979, the MK 6 semiclosed-circuit underwater breathing apparatus
(UBA) was phased out by the MK 15 closed-circuit, constant oxygen partial pres-
sure UBA. The Navy Experimental Diving Unit developed decompression
procedures for the MK 15 with nitrogen and helium in the early 1980s. In 1985, an
improved low magnetic signature version of the MK 15, the MK 16, was approved
for Explosive Ordnance Disposal (EOD) team use.
Scuba Use During World War II.
Although closed-circuit equipment was re-
stricted to shallow-water use and carried with it the potential danger of oxygen
toxicity, its design had reached a suitably high level of efficiency by World War II.
During the war, combat swimmer breathing units were widely used by navies on
both sides of the conflict. The swimmers used various modes of underwater attack.
Many notable successes were achieved including the sinking of several battle-
ships, cruisers, and merchant ships.
using closed-circuit gear, rode chariot torpe-
does fitted with seats and manual controls in
repeated attacks against British ships. In
1936, the Italian Navy tested a chariot tor-
pedo system in which the divers used a de-
scendant of the Fleuss scuba. This was the
Davis Lung (Figure 1-10). It was originally
designed as a submarine escape device and
was later manufactured in Italy under a li-
cense from the English patent holders.
British divers, carried to the scene of action
in midget submarines, aided in placing
explosive charges under the keel of the
German battleship Tirpitz. The British began
their chariot program in 1942 using the
Davis Lung and exposure suits. Swimmers
using the MK 1 chariot dress quickly discov-
Submerged Escape Apparatus.
1-14 U.S. Navy Diving Manual—Volume 1
ered that the steel oxygen bottles adversely affected the compass of the chariot
torpedo. Aluminum oxygen cylinders were not readily available in England, but
German aircraft used aluminum oxygen cylinders that were almost the same size
as the steel cylinders aboard the chariot torpedo. Enough aluminum cylinders were
salvaged from downed enemy bombers to supply the British forces.
Changes introduced in the MK 2 and MK 3 diving dress involved improvements
in valving, faceplate design, and arrangement of components. After the war, the
MK 3 became the standard Royal Navy shallow water diving dress. The MK 4
dress was used near the end of the war. Unlike the MK 3, the MK 4 could be
supplied with oxygen from a self-contained bottle or from a larger cylinder carried
in the chariot. This gave the swimmer greater endurance, yet preserved freedom of
movement independent of the chariot torpedo.
In the final stages of the war, the Japanese employed an underwater equivalent of
their kamikaze aerial attack—the kaiten diver-guided torpedo.
U.S. Combat Swimming.
There were two groups of U.S. combat swimmers
during World War II: Naval beach reconnaissance swimmers and U.S. operational
swimmers. Naval beach reconnaissance units did not normally use any breathing
devices, although several models existed.
U.S. operational swimmers, however,
under the Office of Strategic Services,
developed and applied advanced methods
for true self-contained diver-submersible
operations. They employed the
Lambertsen Amphibious Respiratory
Unit (LARU), a rebreather invented by
Dr. C.J. Lambertsen (see Figure 1-11).
The LARU was a closed-circuit oxygen
UBA used in special warfare operations
where a complete absence of exhaust
bubbles was required. Following World
War II, the Emerson-Lambertsen Oxygen
Rebreather replaced the LARU (Figure
1-12). The Emerson Unit was used exten-
sively by Navy special warfare divers
until 1982, when it was replaced by the
Draeger Lung Automatic Regenerator
(LAR) V. The LAR V is the standard unit
now used by U.S. Navy combat swim-
mers (see Figure 1-13).
Today Navy combat swimmers are organized into two separate groups, each with
specialized training and missions. The Explosive Ordnance Disposal (EOD) team
handles, defuses, and disposes of munitions and other explosives. The Sea, Air
and Land (SEAL) special warfare teams make up the second group of Navy
Respiratory Unit (LARU)
CHAPTER 1 — History of Diving 1-15
combat swimmers. SEAL team members are trained to operate in all of these envi-
ronments. They qualify as parachutists, learn to handle a range of weapons,
receive intensive training in hand-to-hand combat, and are expert in scuba and
other swimming and diving techniques. In Vietnam, SEALs were deployed in
special counter-insurgency and guerrilla warfare operations. The SEALs also
participated in the space program by securing flotation collars to returned space
capsules and assisting astronauts during the helicopter pickup.
The Navy’s Underwater Demolition Teams (UDTs) were
created when bomb disposal experts and Seabees (combat engineers) teamed
together in 1943 to devise methods for removing obstacles that the Germans were
placing off the beaches of France. The first UDT combat mission was a daylight
reconnaissance and demolition project off the beaches of Saipan in June 1944. In
March of 1945, preparing for the invasion of Okinawa, one underwater demolition
team achieved the exceptional record of removing 1,200 underwater obstacles in 2
days, under heavy fire, without a single casualty.
Because suitable equipment was not readily available, diving apparatus was not
extensively used by the UDT during the war. UDT experimented with a modified
Momsen lung and other types of breathing apparatus, but not until 1947 did the
Navy’s acquisition of Aqua-Lung equipment give impetus to the diving aspect of
UDT operations. The trail of bubbles from the open-circuit apparatus limited the
type of mission in which it could be employed, but a special scuba platoon of UDT
members was formed to test the equipment and determine appropriate uses for it.
Through the years since, the mission and importance of the UDT has grown. In the
Korean Conflict, during the period of strategic withdrawal, the UDT destroyed an
Draeger LAR V UBA.
1-16 U.S. Navy Diving Manual—Volume 1
entire port complex to keep it from the enemy. The UDTs have since been incorpo-
rated into the Navy Seal Teams.
Mixed-gas diving operations are conducted using a breathing medium other than
air. This medium may consist of:
Nitrogen and oxygen in proportions other than those found in the atmosphere
A mixture of other inert gases, such as helium, with oxygen.
The breathing medium can also be 100 percent oxygen, which is not a mixed gas,
but which requires training for safe use. Air may be used in some phases of a
Mixed-gas diving is a complex undertaking. A mixed-gas diving operation
requires extensive special training, detailed planning, specialized and advanced
equipment and, in many applications, requires extensive surface-support
personnel and facilities. Because mixed-gas operations are often conducted at
great depth or for extended periods of time, hazards to personnel increase greatly.
Divers studying mixed-gas diving must first be qualified in air diving operations.
In recent years, to match basic operational requirements and capabilities, the U.S.
Navy has divided mixed-gas diving into two categories:
Nonsaturation diving without a pressurized bell to a maximum depth of 300
Saturation diving for dives of 150 fsw and greater depth or for extended
bottom time missions.
The 300-foot limit is based primarily on the increased risk of decompression sick-
ness when nonsaturation diving techniques are used deeper than 300 fsw.
An inventor named Elihu Thomson theorized that
helium might be an appropriate substitute for the nitrogen in a diver’s breathing
supply. He estimated that at least a 50-percent gain in working depth could be
achieved by substituting helium for nitrogen. In 1919, he suggested that the U.S.
Bureau of Mines investigate this possibility. Thomson directed his suggestion to
the Bureau of Mines rather than the Navy Department, since the Bureau of Mines
held a virtual world monopoly on helium marketing and distribution.
Experiments with Helium-Oxygen Mixtures.
In 1924, the Navy and the Bureau of
Mines jointly sponsored a series of experiments using helium-oxygen mixtures.
The preliminary work was conducted at the Bureau of Mines Experimental Station
in Pittsburgh, Pennsylvania. Figure 1-14 is a picture of an early Navy helium-
oxygen diving manifold.
CHAPTER 1 — History of Diving 1-17
The first experiments showed no detrimental effects on test animals or humans
from breathing a helium-oxygen mixture, and decompression time was shortened.
The principal physiological effects noted by divers using helium-oxygen were:
Increased sensation of cold caused by the high thermal conductivity of helium
The high-pitched distortion or “Donald Duck” effect on human speech that
resulted from the acoustic properties and reduced density of the gas
These experiments clearly showed that helium-oxygen mixtures offered great
advantages over air for deep dives. They laid the foundation for developing the
reliable decompression tables and specialized apparatus, which are the corner-
stones of modern deep diving technology.
In 1937, at the Experimental Diving Unit research facility, a diver wearing a deep-
sea diving dress with a helium-oxygen breathing supply was compressed in a
chamber to a simulated depth of 500 feet. The diver was not told the depth and
when asked to make an estimate of the depth, the diver reported that it felt as if he
were at 100 feet. During decompression at the 300-foot mark, the breathing
mixture was switched to air and the diver was troubled immediately by nitrogen
The first practical test of helium-oxygen came in 1939, when the submarine USS
Squalus was salvaged from a depth of 243 fsw. In that year, the Navy issued
decompression tables for surface-supplied helium-oxygen diving.
Helium-Oxygen Diving Manifold.
1-18 U.S. Navy Diving Manual—Volume 1
MK V MOD 1 Helmet.
was expensive and shipboard supplies
were limited, the standard MK V MOD 0
open-circuit helmet was not economical
for surface-supplied helium-oxygen
diving. After experimenting with several
different designs, the U.S. Navy adopted
the semiclosed-circuit MK V MOD 1
The MK V MOD 1 helmet was equipped
with a carbon dioxide absorption canister
and venturi-powered recirculator
assembly. Gas in the helmet was continu-
ously recirculated through the carbon
dioxide scrubber assembly by the
venturi. By removing carbon dioxide by
scrubbing rather than ventilating the
helmet, the fresh gas flow into the helmet
was reduced to the amount required to
replenish oxygen. The gas consumption
of the semiclosed-circuit MK V MOD 1 was approximately 10 percent of that of
the open-circuit MK V MOD 0.
The MK V MOD 1, with breastplate and recirculating gas canister, weighed
approximately 103 pounds compared to 56 pounds for the standard air helmet and
breastplate. It was fitted with a lifting ring at the top of the helmet to aid in hatting
the diver and to keep the weight off his shoulders until he was lowered into the
water. The diver was lowered into and raised out of the water by a diving stage
connected to an onboard boom.
U.S. Navy divers were not alone in working with mixed gases
or helium. In 1937, civilian engineer Max Gene Nohl reached 420 feet in Lake
Michigan while breathing helium-oxygen and using a suit of his own design. In
1946, civilian diver Jack Browne, designer of the lightweight diving mask that
bears his name, made a simulated helium-oxygen dive of 550 feet. In 1948, a
British Navy diver set an open-sea record of 540 fsw while using war-surplus
helium provided by the U.S.
In countries where the availability of helium was more
restricted, divers experimented with mixtures of other gases. The most notable
example is that of the Swedish engineer Arne Zetterstrom, who worked with
hydrogen-oxygen mixtures. The explosive nature of such mixtures was well
known, but it was also known that hydrogen would not explode when used in a
mixture of less than 4 percent oxygen. At the surface, this percentage of oxygen
would not be sufficient to sustain life; at 100 feet, however, the oxygen partial
pressure would be the equivalent of 16 percent oxygen at the surface.
MK V MOD 1 Helmet.
CHAPTER 1 — History of Diving 1-19
Zetterstrom devised a simple method for making the transition from air to
hydrogen-oxygen without exceeding the 4-percent oxygen limit. At the 100-foot
level, he replaced his breathing air with a mixture of 96 percent nitrogen and 4
percent oxygen. He then replaced that mixture with hydrogen-oxygen in the same
proportions. In 1945, after some successful test dives to 363 feet, Zetterstrom
reached 528 feet. Unfortunately, as a result of a misunderstanding on the part of
his topside support personnel, he was brought to the surface too rapidly. Zetter-
strom did not have time to enrich his breathing mixture or to adequately
decompress and died as a result of the effects of his ascent.
Modern Surface-Supplied Mixed-Gas Diving.
The U.S. Navy and the Royal Navy
continued to develop procedures and equipment for surface-supplied helium-
oxygen diving in the years following World War II. In 1946, the Admiralty Exper-
imental Diving Unit was established and, in 1956, during open-sea tests of helium-
oxygen diving, a Royal Navy diver reached a depth of 600 fsw. Both navies
conducted helium-oxygen decompression trials in an attempt to develop better
In the early 1960s, a young diving enthusiast from Switzerland, Hannes Keller,
proposed techniques to attain great depths while minimizing decompression
requirements. Using a series of gas mixtures containing varying concentrations of
oxygen, helium, nitrogen, and argon, Keller demonstrated the value of elevated
oxygen pressures and gas sequencing in a series of successful dives in mountain
lakes. In 1962, with partial support from the U.S. Navy, he reached an open-sea
depth of more than 1,000 fsw off the California coast. Unfortunately, this dive was
marred by tragedy. Through a mishap unrelated to the technique itself, Keller lost
consciousness on the bottom and, in the subsequent emergency decompression,
Keller’s companion died of decompression sickness.
By the late 1960s, it was clear that surface-supplied diving deeper than 300 fsw
was better carried out using a deep diving (bell) system where the gas sequencing
techniques pioneered by Hannes Keller could be exploited to full advantage, while
maintaining the diver in a state of comfort and security. The U.S. Navy developed
decompression procedures for bell diving systems in the late 1960s and early
1970s. For surface-supplied diving in the 0-300 fsw range, attention was turned to
developing new equipment to replace the cumbersome MK V MOD 1 helmet.
1-20 U.S. Navy Diving Manual—Volume 1
MK 1 MOD 0 Diving Outfit.
equipment development proceeded along
two parallel paths, developing open-
circuit demand breathing systems suitable
for deep helium-oxygen diving, and
developing an improved recirculating
helmet to replace the MK V MOD 1. By
the late 1960s, engineering improvements
in demand regulators had reduced
breathing resistance on deep dives to
acceptable levels. Masks and helmets
incorporating the new regulators became
commercially available. In 1976, the U.S.
Navy approved the MK 1 MOD 0 Light-
weight, Mixed-Gas Diving Outfit for
dives to 300 fsw on helium-oxygen
(Figure 1-16). The MK 1 MOD 0 Diving
Outfit incorporated a full face mask
(bandmask) featuring a demand open-
circuit breathing regulator and a backpack
for an emergency gas supply. Surface
contact was maintained through an umbil-
ical that included the breathing gas hose, communications cable, lifeline strength
member and pneumofathometer hose. The diver was dressed in a dry suit or hot
water suit depending on water temperature. The equipment was issued as a light-
weight diving outfit in a system with sufficient equipment to support a diving
operation employing two working divers and a standby diver. The outfit was used
in conjunction with an open diving bell that replaced the traditional diver’s stage
and added additional safety. In 1990, the MK 1 MOD 0 was replaced by the MK
21 MOD 1 (Superlite 17 B/NS) demand helmet. This is the lightweight rig in use
In 1985, after an extensive development period, the direct replacement for the
MK V MOD 1 helmet was approved for Fleet use. The new MK 12 Mixed-Gas
Surface-Supplied Diving System (SSDS) was similar to the MK 12 Air SSDS,
with the addition of a backpack assembly to allow operation in a semiclosed-
circuit mode. The MK 12 system was retired in 1992 after the introduction of the
MK 21 MOD 1 demand helmet.
Although open, pressure-balanced diving bells have been used for
several centuries, it was not until 1928 that a bell appeared that was capable of
maintaining internal pressure when raised to the surface. In that year, Sir Robert
H. Davis, the British pioneer in diving equipment, designed the Submersible
Decompression Chamber (SDC). The vessel was conceived to reduce the time a
diver had to remain in the water during a lengthy decompression.
The Davis SDC was a steel cylinder capable of holding two men, with two inward-
opening hatches, one on the top and one on the bottom. A surface-supplied diver
MK 1 MOD 0 Diving Outfit
CHAPTER 1 — History of Diving 1-21
was deployed over the side in the normal mode and the bell was lowered to a depth
of 60 fsw with the lower hatch open and a tender inside. Surface-supplied air
ventilated the bell and prevented flooding. The diver’s deep decompression stops
were taken in the water and he was assisted into the bell by the tender upon arrival
at 60 fsw. The diver’s gas supply hose and communications cable were removed
from the helmet and passed out of the bell. The lower door was closed and the bell
was lifted to the deck where the diver and tender were decompressed within the
safety and comfort of the bell.
By 1931, the increased decompression times associated with deep diving and the
need for diver comfort resulted in the design of an improved bell system. Davis
designed a three-compartment deck decompression chamber (DDC) to which the
SDC could be mechanically mated, permitting the transfer of the diver under pres-
sure. The DDC provided additional space, a bunk, food and clothing for the
diver’s comfort during a lengthy decompression. This procedure also freed the
SDC for use by another diving team for continuous diving operations.
The SDC-DDC concept was a major advance in diving safety, but was not applied
to American diving technology until the advent of saturation diving. In 1962, E. A.
Link employed a cylindrical, aluminum SDC in conducting his first open-sea satu-
ration diving experiment. In his experiments, Link used the SDC to transport the
diver to and from the sea floor and a DDC for improved diver comfort. American
diving had entered the era of the Deep Diving System (DDS) and advances and
applications of the concept grew at a phenomenal rate in both military and
As divers dove deeper and attempted more ambitious under-
water tasks, a safe method to extend actual working time at depth became crucial.
Examples of saturation missions include submarine rescue and salvage, sea bed
implantments, construction, and scientific testing and observation. These types of
operations are characterized by the need for extensive bottom time and, conse-
quently, are more efficiently conducted using saturation techniques.
Advantages of Saturation Diving.
In deep diving operations, decompression is
the most time-consuming factor. For example, a diver working for an hour at 200
fsw would be required to spend an additional 3 hours and 20 minutes in the water
undergoing the necessary decompression.
However, once a diver becomes saturated with the gases that make decompression
necessary, the diver does not need additional decompression. When the blood and
tissues have absorbed all the gas they can hold at that depth, the time required for
decompression becomes constant. As long as the depth is not increased, additional
time on the bottom is free of any additional decompression.
If a diver could remain under pressure for the entire period of the required task, the
diver would face a lengthy decompression only when completing the project. For a
40-hour task at 200 fsw, a saturated diver would spend 5 days at bottom pressure
1-22 U.S. Navy Diving Manual—Volume 1
and 2 days in decompression, as opposed to spending 40 days making 1-hour dives
with long decompression periods using conventional methods.
The U.S. Navy developed and proved saturation diving techniques in its Sealab
series. Advanced saturation diving techniques are being developed in ongoing
programs of research and development at the Navy Experimental Diving Unit
(NEDU), Navy Submarine Medical Research Laboratory (NSMRL), and many
institutional and commercial hyperbaric facilities. In addition, saturation diving
using Deep Diving Systems (DDS) is now a proven capability.
Bond’s Saturation Theory.
True scientific impetus was first given to the satura-
tion concept in 1957 when a Navy diving medical officer, Captain George F.
Bond, theorized that the tissues of the body would eventually become saturated
with inert gas if exposure time was long enough. Bond, then a commander and the
director of the Submarine Medical Center at New London, Connecticut, met with
Captain Jacques-Yves Cousteau and determined that the data required to prove the
theory of saturation diving could be developed at the Medical Center.
With the support of the U.S. Navy, Bond initiated the Genesis
Project to test the theory of saturation diving. A series of experiments, first with
test animals and then with humans, proved that once a diver was saturated, further
extension of bottom time would require no additional decompression time. Project
Genesis proved that men could be sustained for long periods under pressure, and
what was then needed was a means to put this concept to use on the ocean floor.
Several test dives were conducted in the early 1960s:
The first practical open-sea demonstrations of saturation diving were
undertaken in September 1962 by Edward A. Link and Captain Jacques-Yves
Link’s Man-in-the-Sea program had one man breathing helium-oxygen at 200
fsw for 24 hours in a specially designed diving system.
Cousteau placed two men in a gas-filled, pressure-balanced underwater habitat
at 33 fsw where they stayed for 169 hours, moving freely in and out of their
Cousteau’s Conshelf One supported six men breathing nitrogen-oxygen at 35
fsw for 7 days.
In 1964, Link and Lambertsen conducted a 2-day exposure of two men at 430
Cousteau’s Conshelf Two experiment maintained a group of seven men for 30
days at 36 fsw and 90 fsw with excursion dives to 330 fsw.
The best known U.S. Navy experimental effort in saturation
diving was the Sealab program.
CHAPTER 1 — History of Diving 1-23
Sealabs I and II.
After completing the Genesis Project, the Office of Naval
Research, the Navy Mine Defense Laboratory and Bond’s small staff of volunteers
gathered in Panama City, Florida, where construction and testing of the Sealab I
habitat began in December 1963.
In 1964, Sealab I placed four men underwater for 10 days at an average depth of
192 fsw. The habitat was eventually raised to 81 fsw, where the divers were trans-
ferred to a decompression chamber that was hoisted aboard a four-legged offshore
In 1965, Sealab II put three teams of ten men each in a habitat at 205 fsw. Each
team spent 15 days at depth and one man, Astronaut Scott Carpenter, remained for
30 days (see Figure 1-17).
The follow-on seafloor experiment, Sealab III, was planned for 600
fsw. This huge undertaking required not only extensive development and testing of
equipment but also assessment of human tolerance to high-pressure environments.
To prepare for Sealab III, 28 helium-oxygen saturation dives were performed at
the Navy Experimental Diving Unit to depths of 825 fsw between 1965 and 1968.
In 1968, a record-breaking excursion dive to 1,025 fsw from a saturation depth of
825 fsw was performed at the Navy Experimental Diving Unit (NEDU). The cul-
mination of this series of dives was a 1,000 fsw, 3-day saturation dive conducted
jointly by the U.S. Navy and Duke University in the hyperbaric chambers at Duke.
This was the first time man had been saturated at 1,000 fsw. The Sealab III prepa-
ration experiments showed that men could readily perform useful work at
pressures up to 31 atmospheres and could be returned to normal pressure without
U.S. Navy’s First DDS, SDS-450.
1-24 U.S. Navy Diving Manual—Volume 1
Reaching the depth intended for the Sealab III habitat required highly specialized
support, including a diving bell to transfer divers under pressure from the habitat
to a pressurized deck decompression chamber. The experiment, however, was
marred by tragedy. Shortly after being compressed to 600 fsw in February 1969,
Aquanaut Berry Cannon convulsed and drowned. This unfortunate accident ended
the Navy’s involvement with seafloor habitats.
Research and development continues to extend the depth
limit for saturation diving and to improve the diver’s capability. The deepest dive
attained by the U.S. Navy to date was in 1979 when divers from the NEDU
completed a 37-day, 1,800 fsw dive in its Ocean Simulation Facility. The world
record depth for experimental saturation, attained at Duke University in 1981, is
2,250 fsw, and non-Navy open sea dives have been completed to in excess of 2300
fsw. Experiments with mixtures of hydrogen, helium, and oxygen have begun and
the success of this mixture was demonstrated in 1988 in an open-sea dive to 1,650
Advanced saturation diving techniques are being developed in ongoing programs
of research and development at NEDU, Navy Submarine Medical Research Labo-
ratory (NSMRL), and many institutional and commercial hyperbaric facilities. In
addition, saturation diving using Deep Diving Systems (DDS) is now a proven
Deep Diving Systems (DDS).
Experiments in saturation technique required
substantial surface support as well as extensive underwater equipment. DDS are a
substantial improvement over previous methods of accomplishing deep undersea
work. The DDS is readily adaptable to saturation techniques and safely maintains
the saturated diver under pressure in a dry environment. Whether employed for
saturation or nonsaturation diving, the Deep Diving System totally eliminates long
decompression periods in the water where the diver is subjected to extended envi-
ronmental stress. The diver only remains in the sea for the time spent on a given
task. Additional benefits derived from use of the DDS include eliminating the
need for underwater habitats and increasing operational flexibility for the surface-
The Deep Diving System consists of a Deck Decompression Chamber (DDC)
mounted on a surface-support ship. A Personnel Transfer Capsule (PTC) is mated
to the DDC, and the combination is pressurized to a storage depth. Two or more
divers enter the PTC, which is unmated and lowered to the working depth. The
interior of the capsule is pressurized to equal the pressure at depth, a hatch is
opened, and one or more divers swim out to accomplish their work. The divers can
use a self-contained breathing apparatus with a safety tether to the capsule, or
employ a mask and an umbilical that provides breathing gas and communications.
Upon completing the task, the divers enters the capsule, close the hatch and return
to the support ship with the interior of the PTC still at the working pressure. The
capsule is hoisted aboard and mated to the pressurized DDC. The divers enter the
larger, more comfortable DDC via an entry lock. They remain in the DDC until
CHAPTER 1 — History of Diving 1-25
they must return to the undersea job site. Decompression is carried out comfort-
ably and safely on the support ship.
The Navy developed four deep diving systems: ADS-IV, MK 1 MOD 0, MK 2
MOD 0, and MK 2 MOD 1.
Several years prior to the Sealab I experiment, the Navy successfully de-
ployed the Advanced Diving System IV (ADS-IV) (see Figure 1-18). The ADS-IV
was a small deep diving system with a depth capability of 450 fsw. The ADS-IV
was later called the SDS-450.
MK 1 MOD 0.
The MK 1 MOD 0 DDS was a small system intended to be used on
the new ATS-1 class salvage ships, and underwent operational evaluation in 1970.
The DDS consisted of a Personnel Transfer Capsule (PTC) (see Figure 1-19), a
life-support system, main control console and two deck decompression chambers
to handle two teams of two divers each. This system was also used to operationally
evaluate the MK 11 UBA, a semiclosed-circuit mixed-gas apparatus, for saturation
diving. The MK 1 MOD 0 DDS conducted an open-sea dive to 1,148 fsw in 1975.
The MK 1 DDS was not installed on the ATS ships as originally planned, but
placed on a barge and assigned to Harbor Clearance Unit Two. The system went
out of service in 1977.
MK 2 MOD 0.
The Sealab III experiment required a much larger and more capable
deep diving system than the MK 1 MOD 0. The MK 2 MOD 0 was constructed
and installed on the support ship Elk River (IX-501). With this system, divers
could be saturated in the deck chamber under close observation and then trans-
ported to the habitat for the stay at depth, or could cycle back and forth between
the deck chamber and the seafloor while working on the exterior of the habitat.
DDS MK 1 Personnel Transfer Capsule.
PTC Handling System,
1-26 U.S. Navy Diving Manual—Volume 1
The bell could also be used in a non-pressurized observation mode. The divers
would be transported from the habitat to the deck decompression chamber, where
final decompression could take place under close observation.
MK 2 MOD 1.
Experience gained with the MK 2 MOD 0 DDS on board Elk River
(IX-501) (see Figure 1-20) led to the development of the MK 2 MOD 1, a larger,
more sophisticated DDS. The MK 2 MOD 1 DDS supported two four-man teams
for long term saturation diving with a normal depth capability of 850 fsw. The
diving complex consisted of two complete systems, one at starboard and one at
port. Each system had a DDC with a life-support system, a PTC, a main control
console, a strength-power-communications cable (SPCC) and ship support. The
two systems shared a helium-recovery system. The MK 2 MOD 1 was installed on
the ASR 21 Class submarine rescue vessels.
SUBMARINE SALVAGE AND RESCUE
At the beginning of the 20th century, all major navies turned their attention toward
developing a weapon of immense potential—the military submarine. The highly
effective use of the submarine by the German Navy in World War I heightened this
interest and an emphasis was placed on the submarine that continues today.
The U.S. Navy had operated submarines on a limited basis for several years prior
to 1900. As American technology expanded, the U.S. submarine fleet grew
rapidly. However, throughout the period of 1912 to 1939, the development of the
Navy’s F, H, and S class boats was marred by a series of accidents, collisions, and
sinkings. Several of these submarine disasters resulted in a correspondingly rapid
growth in the Navy diving capability.
Until 1912, U.S. Navy divers rarely went below 60 fsw. In that year, Chief Gunner
George D. Stillson set up a program to test Haldane’s diving tables and methods of
stage decompression. A companion goal of the program was to improve Navy
diving equipment. Throughout a 3-year period, first diving in tanks ashore and
then in open water in Long Island Sound from the USS Walkie, the Navy divers
went progressively deeper, eventually reaching 274 fsw.
The experience gained in Stillson’s program was put to dramatic use in
1915 when the submarine USS F-4 sank near Honolulu, Hawaii. Twenty-one men
lost their lives in the accident and the Navy lost its first boat in 15 years of subma-
rine operations. Navy divers salvaged the submarine and recovered the bodies of
the crew. The salvage effort incorporated many new techniques, such as using
lifting pontoons. What was most remarkable, however, was that the divers
completed a major salvage effort working at the extreme depth of 304 fsw, using
air as a breathing mixture. The decompression requirements limited bottom time
for each dive to about 10 minutes. Even for such a limited time, nitrogen narcosis
made it difficult for the divers to concentrate on their work.
The publication of the first U.S. Navy Diving Manual and the establishment of a
Navy Diving School at Newport, Rhode Island, were the direct outgrowth of expe-
CHAPTER 1 — History of Diving 1-27
rience gained in the test program and the USS F-4 salvage. When the U.S. entered
World War I, the staff and graduates of the school were sent to Europe, where they
conducted various salvage operations along the coast of France.
The physiological problems encountered in the salvage of the USS F-4 clearly
demonstrated the limitations of breathing air during deep dives. Continuing
concern that submarine rescue and salvage would be required at great depth
focused Navy attention on the need for a new diver breathing medium.
In September of 1925, the USS S-51 submarine was rammed by a
passenger liner and sunk in 132 fsw off Block Island, Rhode Island. Public pres-
sure to raise the submarine and recover the bodies of the crew was intense. Navy
diving was put in sharp focus, realizing it had only 20 divers who were qualified to
go deeper than 90 fsw. Diver training programs had been cut at the end of World
War I and the school had not been reinstituted.
Salvage of the USS S-51 covered a 10-month span of difficult and hazardous
diving, and a special diver training course was made part of the operation. The
submarine was finally raised and towed to the Brooklyn Navy Yard in New York.
Interest in diving was high once again and the Naval School, Diving and Salvage,
was reestablished at the Washington Navy Yard in 1927. At the same time, the
Navy brought together its existing diving technology and experimental work by
shifting the Experimental Diving Unit (EDU), which had been working with the
Bureau of Mines in Pennsylvania, to the Navy Yard as well. In the following
years, EDU developed the U.S. Navy Air Decompression Tables, which have
become the accepted world standard and continued developmental work in
helium-oxygen breathing mixtures for deeper diving.
Losing the USS F-4 and USS S-51 provided the impetus for expanding the Navy’s
diving ability. However, the Navy’s inability to rescue men trapped in a disabled
submarine was not confronted until another major submarine disaster occurred.
In 1927, the Navy lost the submarine USS S-4 in a collision with the
Coast Guard cutter USS Paulding. The first divers to reach the submarine in 102
fsw, 22 hours after the sinking, exchanged signals with the men trapped inside.
The submarine had a hull fitting designed to take an air hose from the surface, but
what had looked feasible in theory proved too difficult in reality. With stormy seas
causing repeated delays, the divers could not make the hose connection until it was
too late. All of the men aboard the USS S-4 had died. Even had the hose connec-
tion been made in time, rescuing the crew would have posed a significant problem.
The USS S-4 was salvaged after a major effort and the fate of the crew spurred
several efforts toward preventing a similar disaster. LT C.B. Momsen, a submarine
officer, developed the escape lung that bears his name. It was given its first opera-
tional test in 1929 when 26 officers and men successfully surfaced from an
intentionally bottomed submarine.
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The Navy pushed for development of a rescue chamber that was
essentially a diving bell with special fittings for connection to a submarine deck
hatch. The apparatus, called the McCann-Erickson Rescue Chamber, was proven
in 1939 when the USS Squalus, carrying a crew of 50, sank in 243 fsw. The rescue
chamber made four trips and safely brought 33 men to the surface. (The rest of the
crew, trapped in the flooded after-section of the submarine, had perished in the
The USS Squalus was raised by salvage divers (see Figure 1-21). This salvage and
rescue operation marked the first operational use of HeO
in salvage diving. One
of the primary missions of salvage divers was to attach a down-haul cable for the
Submarine Rescue Chamber (SRC). Following renovation, the submarine,
renamed USS Sailfish, compiled a proud record in World War II.
Just as the loss of the USS F-4, USS S-51, USS S-4 and the
sinking of the USS Squalus caused an increased concern in Navy diving in the
1920s and 1930s, a submarine disaster of major proportions had a profound effect
on the development of new diving equipment and techniques in the postwar
period. This was the loss of the nuclear attack submarine USS Thresher and all her
crew in April 1963. The submarine sank in 8,400 fsw, a depth beyond the survival
limit of the hull and far beyond the capability of any existing rescue apparatus.
An extensive search was initiated to locate the submarine and determine the cause
of the sinking. The first signs of the USS Thresher were located and photographed
a month after the disaster. Collection of debris and photographic coverage of the
wreck continued for about a year.
Two special study groups were formed as a result of the sinking. The first was a
Court of Inquiry, which attributed probable cause to a piping system failure. The
second, the Deep Submergence Review Group (DSRG), was formed to assess the
Navy’s undersea capabilities. Four general areas were examined—search, rescue,
Recovery of the
CHAPTER 1 — History of Diving 1-29
recovery of small and large objects, and the Man-in-the-Sea concept. The basic
recommendations of the DSRG called for a vast effort to improve the Navy’s
capabilities in these four areas.
Deep Submergence Systems Project.
Direct action on the recommendations of
the DSRG came with the formation of the Deep Submergence Systems Project
(DSSP) in 1964 and an expanded interest regarding diving and undersea activity
throughout the Navy.
Submarine rescue capabilities have been substantially improved with the develop-
ment of the Deep Submergence Rescue Vehicle (DSRV) which became
operational in 1972. This deep-diving craft is air-transportable, highly instru-
mented, and capable of diving to 5,000 fsw and rescues to 2,500 fsw.
Three additional significant areas of achievement for the Deep Submergence
Systems Project have been that of Saturation Diving, the development of Deep
Diving Systems, and progress in advanced diving equipment design.
World War II Era.
Navy divers were plunged into the war with the Japanese raid on
Pearl Harbor. The raid began at 0755 on 7 December 1941; by 0915 that same
morning, the first salvage teams were cutting through the hull of the overturned
battleship USS Oklahoma to rescue trapped sailors. Teams of divers worked to
recover ammunition from the magazines of sunken ships, to be ready in the event
of a second attack.
The immense salvage effort that followed at Pearl Harbor was highly successful.
Most of the 101 ships in the harbor at the time of the attack sustained damage. The
battleships, one of the primary targets of the raid, were hardest hit. Six battleships
were sunk and one was heavily damaged. Four were salvaged and returned to the
fleet for combat duty; the former battleships USS Arizona and USS Utah could not
be salvaged. The USS Oklahoma was righted and refloated but sank en route to a
shipyard in the U.S.
Battleships were not the only ships salvaged. Throughout 1942 and part of 1943,
Navy divers worked on destroyers, supply ships, and other badly needed vessels,
often using makeshift shallow water apparatus inside water and gas-filled
compartments. In the Pearl Harbor effort, Navy divers spent 16,000 hours under-
water during 4,000 dives. Contract civilian divers contributed another 4,000
While divers in the Pacific were hard at work at Pearl Harbor, a
major challenge was presented to the divers on the East Coast. The interned
French passenger liner Normandie (rechristened as the USS Lafayette) caught fire
alongside New York City’s Pier 88. Losing stability from the tons of water poured
on the fire, the ship capsized at her berth.
1-30 U.S. Navy Diving Manual—Volume 1
The ship had to be salvaged to clear the vitally needed pier. The Navy took advan-
tage of this unique training opportunity by instituting a new diving and salvage
school at the site. The Naval Training School (Salvage) was established in
September 1942 and was transferred to Bayonne, New Jersey in 1946.
Other Diving Missions.
Salvage operations were not the only missions assigned
to Navy divers during the war. Many dives were made to inspect sunken enemy
ships and to recover materials such as code books or other intelligence items. One
Japanese cruiser yielded not only $500,000 in yen, but also provided valuable
information concerning plans for the defense of Japan against the anticipated
Harbor Clearance Unit One (HCU 1) was commissioned 1 February
1966 to provide mobile salvage capability in direct support of combat operations
in Vietnam. Homeported at Naval Base Subic Bay, Philippines, HCU 1 was dedi-
cated primarily to restoring seaports and rivers to navigable condition following
their loss or diminished use through combat action.
Beginning as a small cadre of personnel, HCU 1 quickly grew in size to over 260
personnel, as combat operations in littoral environment intensified. At its peak, the
unit consisted of five Harbor Clearance teams of 20 to 22 personnel each and a
varied armada of specialized vessels within the Vietnam combat zone.
As their World War II predecessors before them, the salvors of HCU 1 left an
impressive legacy of combat salvage accomplishments. HCU 1 salvaged hundreds
of small craft, barges, and downed aircraft; refloated many stranded U.S. Military
and merchant vessels; cleared obstructed piers, shipping channels, and bridges;
and performed numerous underwater repairs to ships operating in the combat
Throughout the colorful history of HCU 1 and her East Coast sister HCU 2, the
vital role salvage forces play in littoral combat operations was clearly demon-
strated. Mobile Diving and Salvage Unit One and Two, the modern-day
descendants of the Vietnam era Harbor Clearance Units, have a proud and distin-
guished history of combat salvage operations.
OPEN-SEA DEEP DIVING RECORDS
Diving records have been set and broken with increasing regularity since the early
. The 300-fsw mark was exceeded. Three U.S. Navy divers, F. Crilley,
W.F. Loughman, and F.C. Nielson, reached 304 fsw using the MK V dress.
. The MK 2 MOD 0 DDS set the in-water record of 1,010 fsw.
. Divers using the MK 1 Deep Dive System descended to 1,148 fsw.
. A French dive team broke the open-sea record with 1,643 fsw.
CHAPTER 1 — History of Diving 1-31
. The deepest salvage operation made with divers was 803 fsw when
British divers retrieved 431 gold ingots from the wreck of HMS Edinburgh,
sunk during World War II.
. Commercial open water diving operations to over 1,000 fsw.
Throughout the evolution of diving, from the earliest breath-holding sponge diver
to the modern saturation diver, the basic reasons for diving have not changed.
National defense, commerce, and science continue to provide the underlying basis
for the development of diving. What has changed and continues to change radi-
cally is diving technology.
Each person who prepares for a dive has the opportunity and obligation to take
along the knowledge of his or her predecessors that was gained through difficult
and dangerous experience. The modern diver must have a broad understanding of
the physical properties of the undersea environment and a detailed knowledge of
his or her own physiology and how it is affected by the environment. Divers must
learn to adapt to environmental conditions to successfully carry out their missions.
Much of the diver’s practical education will come from experience. However,
before a diver can gain this experience, he or she must build a basic foundation
from certain principles of physics, chemistry and physiology and must understand
the application of these principles to the profession of diving.
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