CHAPTER 11 — Ice and Cold Water Diving Operations 11-1
This chapter explains the special requirements for ice and cold water
Polar regions and other cold weather environments are uniquely hostile to
divers, topside support personnel, and equipment. Diving where ice cover is
present can be extremely hazardous and requires special equipment as well as
appropriate operating and support procedures. Awareness of environmental condi-
tions, personnel and equipment selection, and adequate logistical support are vital
to mission success and dive team safety.
Normal diving procedures generally apply to diving in extremely cold environ-
ments. However, there are a number of significant equipment and procedural
differences that enhance the diver’s safety.
The following special planning considerations relate to
diving under/near ice cover or in water at or below a temperature of 37°F:
The task and requirement for ice diving should be reviewed to ascertain that it
is operationally essential.
Environmental conditions such as ice thickness, water depth, temperature,
wind velocity, current, visibility, and light conditions should be determined.
Ideally, a reconnaissance of the proposed dive site is performed by the Diving
Supervisor or a person with ice-covered or cold water diving experience.
The type of dive equipment chosen must be suited for the operation.
Logistical planning must include transportation, ancillary equipment, provi-
sioning, fuel, tools, clothing and bedding, medical evacuation procedures,
NOTE The water temperature of 37°F was set as a limit as a result of Naval
ulator freeze-up testin
. For plannin
uidance above may also be used for divin
water temperature is above 37°F.
Conditions in cold and ice-covered water affect
diver underwater navigation in the following ways:
11-2 U.S. Navy Diving Manual—Volume 2
The proximity of the magnetic pole in polar regions makes the magnetic com-
The life of batteries in homing beacons, strobes, and communication equip-
ment is shortened when used in cold water.
Surface light is so diffused by ice cover that it is nearly impossible to deter-
mine its source.
Direct ascent to the surface is impossible when under the ice and determining
return direction is often hindered.
In shallow ice-covered waters, detours are often required to circumvent keels
or pressure ridges beneath the ice.
With an ice cover, there are no waves and therefore no ripple patterns on the
bottom to use for general orientation.
Scuba equipment has advantages and disadvantages that
should be considered when planning a cold water dive.
The advantages of using scuba are:
Minimal surface-support requirements
The disadvantages of using scuba are:
Susceptibility of regulator to freezing
Severely limited ability to employ decompression diving techniques
Duration limitations of CO
removal systems in closed-circuit UBA
Refer to the ANU for selection of proper regulator. The
single-hose regulator is susceptible to freezing. The first and/or second stage of the
single-hose regulator may freeze in the free-flow position after a few minutes of
exposure in cold water. The single-hose regulator should be kept in a warm place
before diving. It is important that the diver test the regulator in a warm place, then
refrain from breathing it until submerging. When returning to the surface, the
regulator should remain submerged and the diver should refrain from breathing
from the regulator until resubmerging. The diver’s time on the surface should be
kept to a minimum. Once under the water, chances of a freeze-up are reduced.
However, if a regulator is allowed to free-flow at depth for as little as five seconds,
freeze-up may occur. The diver should therefore avoid purging the second stage of
the regulator when diving in cold water. If water needs to be purged from the
mouthpiece, the diver should do so by exhaling into it (Figure 11-1).
CHAPTER 11 — Ice and Cold Water Diving Operations 11-3
Single-hose regulators should be equipped with an anti-
freeze cap, which is a special first-stage cap that can be filled with liquid silicone
available from the manufacturer. Correct maintenance and application of an
approved lubricant to the appropriate points are also essential. Extra precautions
must also be taken to make sure that scuba cylinders are completely dry inside,
that moisture-free air is used, and that the regulator is thoroughly dried prior to
Octopus and Redundant Regulators.
Where water temperature is at or below
37°F, a redundant scuba system (twin scuba bottles, each having a K-valve and an
approved cold water regulator) or twin scuba bottles with one common manifold
and an approved cold water regulator (with octopus) shall be used.
The use of life preservers is prohibited only when diving under
ice. The accidental inflation of a life preserver will force the diver upward and
may cause a collision with the undersurface of the ice. Should the diver be caught
behind a pressure ridge or other subsurface ice structure, recovery may be difficult
even with tending lines. Also, the exhaust and inlet valves of the variable volume
dry suit will be covered if a life preserver is worn. In the event of a dry suit blow-
up, the inability to reach the exhaust dump valve could cause rapid ascent and
collision with the surface ice.
Ice Diving with Scuba. Divers in Typhoon dry suits and Aga/Divator FFM
Scuba with approved cold-water regulators.
11-4 U.S. Navy Diving Manual—Volume 2
The diver’s mask may show an increased tendency to fog in cold
water. An antifog solution should be used to prevent this from occurring. Saliva
will not prevent cold water fogging.
The minimum equipment required by every Navy scuba diver
for under-ice operations consists of:
Wet suit/variable volume dry suit
Open-circuit scuba with cold water modification or closed-circuit UBA
Weight belt and weights as required
Knife and scabbard
Submersible scuba bottle pressure gauge
Harness such as an Integrated Divers Vest (IDV), MK 12 jocking harness, etc.
A variety of special equipment, such as underwater cameras and lift bags, is avail-
able to divers [see the NAVSEA/00C Authorized for Navy Use (ANU) list for
specific identification of authorized equipment]. However, the effect of extreme
cold on the operation of special equipment must be ascertained prior to use.
Surface-Supplied Diving System (SSDS) Considerations.
Using SSDS in ice-
covered or cold water requires detailed operations planning and extensive logis-
tical support. This includes thermal protection for an elaborate dive station and
recompression chamber and hot water heating equipment. In addition, dive equip-
ment may require cold climate modification. Because of logistical considerations,
scuba is used in most ice diving situations. However, SSDS may be required
because of prolonged bottom times, depth requirements, and complex communi-
cations between topside and diver. When diving in cold water that is not ice
covered, logistic and equipment support requirements are reduced; however, very
cold water poses many of the same dangers to the surface-supplied diver as ice
Advantages and Disadvantages of SSDS.
The advantages of using SSDS are:
Configuration supports bottom-oriented work.
Hot water suit and variable volume dry suit offer diver maximum thermal and
Communications cable offers audio communications.
Gas supply allows maximum duration to the maximum depth limits of diving.
CHAPTER 11 — Ice and Cold Water Diving Operations 11-5
The disadvantages of using SSDS are:
Manifold/panel may freeze up.
Low-pressure compressors do not efficiently remove moisture from the air
which may freeze and clog filters or fracture equipment. This is more likely
when the water is very cold and the air is warm. Banks of high-pressure cylin-
ders may have to be used.
Buildup of air or gas under the ice cover could weaken and fracture thin ice,
endangering tenders, other topside personnel, and equipment.
Movement of ice could foul or drag diver’s umbilical.
Battery life of electronic gear is severely reduced.
Carbon dioxide removal recirculator components may have to be heated.
Decompression under extreme cold conditions may be dangerous due to water
temperature, ice movement, etc.
Effect of Ice Conditions on SSDS.
Ice conditions can prevent or severely affect
surface-supplied diving. In general, the ice field must be stationary and thick
enough to support the dive station and support equipment. If the dive must be
accomplished through an ice floe, the floe must be firmly attached to land or a
stable ice field. Severe ice conditions seriously restrict or prohibit surface-supplied
diving through the ice (i.e., moving, unstable ice or pack ice and bergs, and deep
or jagged pressure ridges could obstruct or trap the diver). In cases where a diver is
deployed from a boat in a fixed mooring, the boat, divers, and divers’ umbilicals
must not be threatened by moving ice floes.
Custom wet suits designed for cold water diving, variable volume
dry suits, and hot water suits have all been used effectively for diving in extremely
cold water. Each has advantages and disadvantages that must be considered when
planning a particular dive mission. All suits must be inspected before use to ensure
they are in good condition with no seam separations or fabric cuts.
Custom wet suits have the advantages of wide availability, simplicity
and less danger of catastrophic failure than dry suits. Although the wet suit is not
the equipment of choice, if used the following should be considered:
The wet suit should be maintained in the best possible condition to reduce
water flushing in and out of the suit.
Wearing heavy insulating socks under the boots in a wet suit will help keep
CAUTION In very cold water, the wet suit is only a mar
inally effective thermal
protective measure, and its use exposes the diver to hypothermia and
11-6 U.S. Navy Diving Manual—Volume 2
restricts available bottom time. The use of alternative thermal protective
equipment should be considered in these circumstances.
Variable Volume Dry Suits.
Variable volume dry suits provide superior thermal
protection to the surface-supplied or scuba diver in the water and on the surface.
They are constructed so the entry zipper or seal and all wrist and neck seals are
waterproof, keeping the interior dry. They can be inflated orally or from a low-
pressure air source via an inlet valve. Air can be exhausted from the suit via a
second valve, allowing excellent buoyancy control. The level of thermal protec-
tion can be varied through careful selection of the type and thickness of long
underwear. However, too much underwear is bulky and can cause overheating,
sweating, and subsequent chilling of the standby diver. Dry suit disadvantages are
increased swimmer fatigue due to suit bulk, possible malfunction of inlet and
exhaust valves, and the need for additional weights for neutral buoyancy. Further-
more, if the diver is horizontal or deployed with the head below the rest of the
body, air can migrate into the suit lower extremities, causing overinflation and loss
of fins and buoyancy control. A parting seam or zipper could result in a dramatic
loss of buoyancy control and thermal shock. Nevertheless, because of its superior
thermal protection, the dry suit is an essential component of extremely cold water
CAUTION Prior to the use of variable volume dry suits and hot water suits in cold
and ice-covered waters, divers must be trained in their use and be
hly familiar with the operation of these suits.
Extreme Exposure Suits/Hot Water Suits.
Hot water suits provide excellent
thermal protection. If their use can be supported logistically, they are an excellent
choice whenever bottom times are lengthy. They are impractical for use by
standby divers exposed on the surface.
A hot water system failure can be catastrophic for a diver in very cold water since
the hot water is a life support system under such conditions. Hot water temperature
must be carefully monitored to ensure that the water is delivered at the proper
temperature. When using the hot water suit, wet suit liners must be worn. The hose
on the surface must be monitored to ensure it does not melt into the ice. When not
in use, the heater and hoses must be thoroughly drained and dried to prevent
freezing and rupture.
Proper planning must include protecting tenders and topside support
personnel from the environment. However, bulky clothing and heavy mittens
make even routine tasks difficult for topside personnel. Waterproof outer gloves
and boots may also be considered. Regardless of the type of clothing selected, the
clothing must be properly fitted (loosely worn), and kept clean and dry to maxi-
mize insulation. In planning operations for such conditions, reduced efficiency
resulting in longer on-site time must be considered. Refer to the Polar Operations
Manual for complete information on thermal protection of support personnel and
CHAPTER 11 — Ice and Cold Water Diving Operations 11-7
A detailed reconnaissance of the dive site will provide the
planner with information that is helpful in deciding what ancillary equipment is
required. Diving under ice will require special accessory equipment such as a line
with lights for underwater navigation, ice-cutting tools, platforms, and engine
The method of cutting the hole through the ice depends on ice thickness and avail-
ability of equipment. Normally, two or more of the following tools are used: hand
ice chipper, ice handsaw, ice auger, chain saw, thermal ice cutter or blasting
equipment. In addition, equipment to lift the ice block, remove the slush, and mark
the hole is required. Sandbags, burlap bags, or pallets for the tenders to stand on
are also needed. Ladders should be in place in case a tender falls into the hole.
If there is a possibility of surface support personnel falling through the ice, float-
able work platforms, such as an inflated Zodiac boat, should be used. With such
flotation equipment, the operation could be continued or safely concluded if the
ice breaks up.
Gasoline and diesel engines must be cold-weather modified to prevent engine
freeze-up. Vibrations of engines running on the ice can be a problem and vibration
dampening platforms may be required.
Dive Site Shelter.
Tent equipment including framing and flooring material may
be required to construct a dive site shelter and a windbreak. Depending on the
severity of the climate, remoteness of the site, and duration of the mission, shelters
can range from small tents to steel sea-land vans and elaborate insulated huts
transported to the site and erected from kits. Dive site shelters should have storage
areas for dry items and a place for drying equipment. Benches should be provided
for dressing divers, flooring should be installed for insulation, and heating and
lighting should be adequate. In an extremely cold and dry climate, fire and inade-
quate ventilation are ever-present dangers. A carbon monoxide detection kit
should be available and periodic checks made of all living and working spaces.
Fire extinguishers shall be available in each shelter.
The supervisor of the dive must ensure that all
personnel required to make the dive have been properly trained in ice diving tech-
niques and are physically fit. No diver may be allowed to make the dive if, in the
opinion of the Diving Supervisor, the diver is suffering from the psychological
stress of an ice dive (anxiety, claustrophobia, or recklessness).
Dive Site Selection Considerations.
The selection of the dive site will depend
upon the purpose of the dive and the geographical environment of the area (ice
thickness, ice surface conditions, etc.). Additionally, the diving method chosen,
safe access routes, shelter location, emergency holes, and exposure of divers and
required support personnel will also have a bearing on site selection.
11-8 U.S. Navy Diving Manual—Volume 2
When ice diving is conducted, a shelter must be erected as close as
possible to the diving site to reduce the probability of frostbite and equipment
freeze-up. Normally, tents are not placed over the dive hole because they would
restrict the movement of tenders and light available to the diver. However, a wind-
break should be constructed. A shelter of modular tents and space heaters is ideal;
although precautions must be taken to ensure that the ice beneath the shelter is not
weakened. Extreme caution must be used when diving for objects, such as downed
aircraft, that have fallen through the ice; the area around the original hole may be
Proper equipment should be used to cut a suitable hole or holes
through the ice in order to leave a clean edge around the hole. Using a sledge-
hammer to break through the ice is not recommended as it will weaken the
surrounding ice. The hole should be a rectangle 6 feet by 3 feet, or a triangle with
six-foot sides as shown in Figure 11-2. The triangular hole is easier to cut and is
large enough to allow simultaneous exit by two divers. Slush and ice must be
removed from the hole, not pushed under the ice surface, as it could slip back and
block the hole. To assist exiting divers and improve footing for other team
members on the ice surface, sand or burlap bags should be placed on the ice
around the hole. Upon completing the dive, the hole must be clearly marked to
prevent anyone from falling in accidentally. When possible, the pieces cut from
the ice should be replaced to speed up the refreezing process.
Escape holes provide alternative exit points and aid in searching
for a lost diver. Downstream escape holes or emergency exit holes must be cut in
the ice when diving in a river or bay where there is a current or tidal stream.
A weighted line should be hung through the hole to aid the
diver in retaining his bearing and sense of direction. Suspending a light at the end
of the line may be helpful, as well as attaching a series of strobe lights to indicate
depth. After locating the work site, a distance line should be laid from the
weighted line to the work site. Another method of aiding the diver in keeping his
bearings in clear water is to shovel off the snow cover on the ice around the dive
site in the form of a spoked wheel (see Figure 11-2). When the ice and snow cover
is less than 2 feet thick, the diver should be able to see the spokes leading to the
dive hole located at the center of the wheel. The wheel should have a minimum
diameter of 60 feet.
Diver tending lines are mandatory when diving under ice to help the
diver relocate the entrance hole. A polypropylene braided or twisted line has
proven to be the best lifeline. It has the advantage of floating up and away from
the diver and is available in yellow, white, and orange for high visibility. A
bowline or a D-ring and snap hook spliced into the lifeline is the easiest method of
attaching the lifeline to the diver. The attachment of the lifeline on both ends must
be absolutely secure. Do not tie the line to a vehicle, shovel, first-aid box, or other
portable equipment. A 4-inch by 4-inch by 2-foot board placed under the ice
several yards away from the dive hole can be used to secure the bitter end of the
lifeline (see Figure 11-2). The D-ring and snap hook allow the quickest transfer of
CHAPTER 11 — Ice and Cold Water Diving Operations 11-9
the lifeline from diver to diver on the surface, provided the snap hooks are not
frozen shut. The snap hooks should be checked for corrosion at frequent intervals.
A wet lifeline must be kept off the bare ice to prevent it from freezing to the
The diver must wear a distress light that should be
turned on upon entering the water. Divers should not be encumbered with unnec-
essary equipment during cold water dives. Snorkels should be removed and knives
worn on the inside of the leg to help prevent the lifeline from snagging on the
diver’s equipment. Personnel, divers, and tenders must handle rubber accessories
such as masks and fins carefully; extreme cold causes them to become brittle.
Diving under the ice or in extremely cold waters requires the use
of paired dive partners. Buddy diving is required, despite the fact that each diver
must be surface tended. When diving through the ice, divers shall always be
Typical Ice Diving Worksite.
11-10 U.S. Navy Diving Manual—Volume 2
surface tended. The life-threatening consequences of suit failure, regulator freeze-
up or other equipment problems make a solitary tended scuba diver particularly
vulnerable. Divers must practice buddy breathing prior to the operation because of
the increased possibility that buddy breathing will be required. Proficiency in the
process will minimize loss of valuable time during an emergency. Using approved
cold water scuba equipment will minimize or eliminate freeze-up problems (see
Tending the Diver.
The lifeline is to be held by the tender at all times. As an addi-
tional safety measure during ice diving, the end of the lifeline must be secured to a
stationary object to prevent it from falling into the entry hole should it be dropped
by the tender (see Figure 11-2). It is recommended that the lifeline be marked at
10-foot intervals to allow the tender and Diving Supervisor to estimate the diver’s
position. However, the diver’s radial position can only be roughly estimated. The
dive team must be thoroughly familiar with the procedures for lifeline tending in
Tending line sensitivity and awareness of the diver’s position by tenders may be
difficult with the added factors of lifeline drag on subsurface ice formations, line
drag over the lip of the under-ice hole, tending through heavy mittens, and the lack
of surface bubbles.
The standby diver and tender must be immediately available. The
standby diver should be kept warm until the Diving Supervisor determines that the
standby diver is needed. If possible a shelter or windbreak at the hole should be
used. The lifeline of the standby diver should be twice the length of the diver’s
lifeline in order to perform a thorough circular search. The standby diver must be
dressed with the exception of fins, mask, and tanks. These will be ready to don
Normal procedures generally apply to diving in extremely cold environments.
However, the increased likelihood of regulator freeze-up calls for total familiarity
with the buddy breathing procedures described in Chapter 7. This section outlines
some of the precautions for operating in cold and ice-covered water.
General precautions for ice and cold water diving opera-
Divers should be well rested, have a meal high in carbohydrates and protein,
and should not consume any alcohol. Alcohol dilates the blood vessels in the
skin, thus increasing body heat loss.
Bathing is an important health measure to prevent infectious diseases preva-
lent in cold environments. If necessary, the body can be sponge-bathed under
CHAPTER 11 — Ice and Cold Water Diving Operations 11-11
After bathing, a soothing ointment or lotion should be applied to the skin to
keep it soft and protect it against evaporation caused by the dry air.
Shaving and washing the face should be done in the evening because shaving
removes protective oils from the skin. Shaving too close can also remove
some of the protective layer of the skin, promoting frostbite.
The inconsistency and dynamics of ice conditions in any partic-
ular area can make diving operations extremely hazardous. The movement of ice
floes can be very significant over a relatively short period of time, requiring
frequent relocation of dive sites and the opening of new access holes in order to
work a fixed site on the sea floor. Diving from drifting ice or in the midst of
broken free ice is dangerous and should be conducted only if absolutely necessary.
Differential movement of surface and subsurface pressure ridges or icebergs could
close an access hole, sever a diving umbilical, and isolate or crush a diver. The
opening of a rift in the ice near a dive site could result in loss of support facilities
on the ice, as well as diver casualties.
With a properly fitting suit and all seals in place, the diver
can usually be kept warm and dry for short periods in even the coldest water.
When dressing for an ice or cold water dive:
Thermal protection suits should be checked carefully for fabric cuts and sepa-
rations. Thermal protection suits should expose only a minimum of facial area.
Mittens, boots, and seals should prevent water entry, while causing no restric-
tion of circulation. Wearing a knitted watchcap under the hood of a dry suit is
effective in conserving body heat. With the cap pushed back far enough to per-
mit the suit’s face seal to seat properly, the head will be relatively dry and
While on the surface:
Suited divers should be protected from overheating and associated perspiring
before entering the water. Overheating easily occurs when operating from a
heated hut, especially if diver exertion is required to get to the dive site. The
divers’ comfort can be improved and sweating delayed before entering the
water by cooling the divers face with a damp cloth and fanning every few min-
utes. Perspiration will dampen undergarments, greatly reducing their thermal
While waiting to enter the water, divers should avoid sitting on or resting their
feet on the ice or cold floor of a hut. Even in an insulated hut, the temperature
at the floor may be near freezing.
Time on the surface with the diver suited, but relatively inactive, should be
minimized to prevent chilling of the diver. Surface time can also cool metal
components of the diving gear, such as suit valves and scuba regulators, below
11-12 U.S. Navy Diving Manual—Volume 2
the freezing point and cause the parts to ice up when the diver enters the water.
Dressing rehearsals prior to diving will help minimize surface delays.
When operating from an open boat, heavy parkas or windbreakers should be
worn over the exposure suits.
When operating at the surface in newly formed ice, care should be taken to
avoid cutting exposed facial skin. Such wounds occur easily and, although
painless because of the numbness of the skin, usually bleed profusely.
Diving from a beach and without a support vessel should be limited to a dis-
tance that allows the divers to return to the beach if the suit floods.
Extreme caution must be exercised when diving near ice keels in polar regions
as they will often move with tidal action, wind, or current. In doing so, they
can foul umbilicals and jeopardize the divers’ safety.
Because severe chilling can result in impaired judgment, the tasks to be per-
formed under water must be clearly identified, practiced, and kept simple.
A dive should be terminated upon the onset of involuntary shivering or severe
impairment of manual dexterity.
If the exposure suit tears or floods, the diver should surface immediately,
regardless of the degree of flooding. The extreme chilling effect of frigid water
can cause thermal shock within minutes, depending on the extent of flooding.
Divers and Diving Supervisors must be aware of the cumulative thermal effect
of repetitive diving. A thermal debt can accumulate over successive diving
days, resulting in increased fatigue and reduced performance. The progressive
hypothermia associated with long, slow cooling of the body appears to cause
significant core temperature drop before shivering and heat production begins.
Upon exiting cold water, a diver will probably be fatigued
and greatly susceptible to additional chilling:
If a wet suit was worn, immediate flushing with warm water upon surfacing
will have a comforting, heat-replacing effect.
Facilities must be provided to allow the diver to dry off in a comfortable, dry
and relatively warm environment to regain lost body heat.
The diver should remove any wet dress, dry off, and don warm protective
clothing as soon as possible. Personnel should have warm, dry clothing, blan-
kets, and hot non-alcoholic beverages available to them.
CHAPTER 11 — Ice and Cold Water Diving Operations 11-13
A diver who becomes detached from the lifeline and cannot locate the
entrance hole should:
Ascend to the underside of the ice.
Remove weight belt and allow it to drop.
Fix the point of the knife into the ice to maintain position.
Remain in a vertical position, to maximize vertical profile and thereby snag
the searching standby diver’s lifeline.
Watch for lifeline and the lifeline of the standby diver and wait for the standby
diver to arrive. The lost diver MUST NOT attempt to relocate the hole. The
diver must remain calm and watch for the standby diver.
Searching for a Lost Diver.
As soon as the tender fails to get a response from the
diver, the tender must notify the Diving Supervisor immediately. These proce-
dures are to be implemented at once:
The Diving Supervisor shall immediately recall all other divers.
The Diving Supervisor must estimate the probable location of the lost diver by
assessing the diver’s speed and direction of travel.
As directed by the Diving Supervisor, the standby diver enters the water and
swims in the indicated direction, a distance equal to twice that believed to be
covered by the lost diver. The distance may be the full extent of the standby
diver’s lifeline since it is twice as long as the lost diver’s lifeline.
The tender must keep the standby diver’s lifeline taut.
The standby diver conducts a circular sweep.
When the lifeline snags on the lost diver, the standby diver swims toward the
diver signaling the tender to take up slack.
Upon locating the lost diver, the standby diver assists the diver back to the
If the first sweep fails, it should be repeated only once before moving the
search to the most likely emergency hole.
When diving in cold water, hypothermia may predispose the diver
to decompression sickness. Hypothermia is easily diagnosed. The hypothermic
diver loses muscle strength, the ability to concentrate and may become irrational
or confused. The victim may shiver violently, or, with severe hypothermia, shiv-
ering may be replaced by muscle rigidity. Profound hypothermia may so depress
11-14 U.S. Navy Diving Manual—Volume 2
the heartbeat and respiration that the victim appears dead. However, a diver should
not be considered dead until the diver has been rewarmed and all resuscitation
attempts have been proven to be unsuccessful.
Hypothermia demands immediate treatment and prompt evacuation to a medical
facility. A hypothermic diver must not be allowed to walk; the diver should be
transported in a horizontal position. Improper handling of the diver can cause
dangerous rhythms of the heart and a drop in the body core temperature, known as
For information on extreme cold weather conditions and the polar environment,
A Guide to Extreme Cold Weather Operations (Naval Safety Center, July
Polar Operations Manual S0300-A5-MAN-010 (Naval Coastal Systems Cen-
Guide to Polar Diving (Office of Naval Research, June 1976)
UCT Arctic Operation Manual NAVFAC P-992
(To obtain a copy of this manual, contact NCSC, Code 5110.)