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HomeScuba DivingCold Comfort - Part II

Cold Comfort – Part II

This article does not present the complete picture of ice diving and does not replace proper training and experience.  If the reader wishes to participate in ice diving or extreme cold water diving, they should take an ice diving course as well as a course on overhead environments like cave or wreck penetration.

Part I of Cold Comfort introduced the reader to ice diving and suggested various ways of handling a cold climate plus techniques to improve safety and expand the scope of the dive. We know cold can have adverse affects on the mental and physical well being of a diver and precautions are needed to reduce the level of exposure.

Gear is equally as susceptible to attacks from the cold. Freezing temperatures will cause regulators to free flow, dry suits, gloves and hoods to shrink in size. O-rings, latex seals and plastic buckles become brittle and can easily be torn or broken.  Batteries in computers, bottom timers and lights can die or have a reduced burn times. LCD screens in computers/bottom timers can freeze and stop displaying information.

Cold may indirectly affect your kit as well. All the water on your gear will suddenly freeze when exposed to the air, making it nearly impossible to get out of. Exposed skin can freeze to metal parts, like manifolds or d-rings, and damage can occur because of slipping on ice or dropping out of gloved hands.

Like a diver, keeping the gear as warm as possible before a dive will greatly improve your diving results and reduce wear and tear. Eventually, however, you will have to expose it to the cold.  While it is impossible to totally avoid gear problems when ice diving, there are ways of bullet-proofing your kit and gear choices that will improve a divers safety and comfort level.


All overhead environments demand a redundant source of gas supply since a diver cannot simply bail out to the surface in case of an emergency. The configuration of choice is a set of twin tanks with two first stage posts connected via a manifold.  Should one regulator malfunction the post can be shutdown and the second one utilized. An isolator on the manifold is also mandatory to be able separate the gas supply in the two tanks. This comes in handy when a particular post cannot be shut down, possibly due to damage, tank o-ring failure, or even freezing in extreme cases.  

A stage bottle, of similar size to one of the twinned bottles, is also recommended. For further explanation see Gas Management below.

Note:All tanks used while ice diving should be low pressure tanks and filled to no more then the recommended pressure ratings, certainly no higher then 3000psi/200bar. High pressures and low temperatures simply do not mix because of the higher risk of cold induced o-ring ruptures and regulator free flows.

Dry Suits 

Dry suits are mandatory pieces of kit for ice diving, wet or even semi dry suits simply do not have the thermal properties to allow a diver to safely stay submerged for any amount of time. It is recommended that a diver uses a shell style dry suit, like a trilam, instead of a neoprene based suit. The big advantages of a shell suit stem form its consistent buoyancy characteristics as there is no compressibility in the outer shell, so if a diver is properly weighted on the surface then they will be properly weighted on the bottom. In general a shell suit usually requires less weight to properly ballast a diver.



There are two kinds of dry suit seals, latex or neoprene. I find that latex does provide a better seal but neoprene tends to be a little softer and provides better insulation. In the end I believe a better water tight seal is the most important factor. However, if a diver gets excellent results with neoprene they should use it.   Also, neoprene may be a little more durable in an extreme cold situation because of its extra thickness, but I have not investigated this.

Thermal Insulation

In an ice environment thermal protection is as important as the gas you are breathing, therefore any loss of thermal protection underwater needs to be treated as catastrophic and a potentially life threatening event. If close to the entrance the diver will usually only suffer extreme discomfort, but if more then 10 minutes away or if there is a need to do several minutes of deco, the situation is more critical. A large enough exposure can cause serious levels of hypothermia in a matter of minutes.

Simply bulking up your insulation does work but it has adverse side effects. It changes the diver’s buoyancy so that extra weight may be needed. It also restricts the mobility of the diver in such a way that a valve closure drill can be nearly impossible to execute.  

A dry suit is only as good as the insulation used in underneath, it makes no sense to spend thousands on a shell and go cheep on the underwear.  In actuality it may be better to get a cheep suit and expensive underwear. Here are some things to look for in good underwear:

  • Warmth rating
    – Should still be good even when wet or damp
  • Wicking properties
    – Should be able to remove moisture away from the body
  • Stretch Ability
    – You should be able to stretch and reach back toward the valves
  • Loft
    – The thicker it is, the warmer it is, but don’t be fooled, underwear gets compressed under a dry suit which may make it less efficient
    – Extra loft may cause buoyancy problems
    – The trick is to get a reasonable loft that gives you good protection even under compression

If unable to find ideal underwear through a dry suit manufacturer, it is possible to find it at stores that cater to mountain climbers, hikers, hunters and anglers. Like many outdoor sports, layering works very well for scuba diving. Having a thin polypropylene (wicking) layer next to the skin, followed by a heat retention layer (fleece) and optionally followed by a vest, is an excellent combination. The vest can be fleece or similar material that adds extra thermal protection around the body core but does not cause binding in the underarms or shoulders, thus making access to those valves a bit easier. Several of my buddies use this layering approach and report excellent winter results.

In addition to underwear divers can use Argon as an inflation gas. Argon is ideally suited as an insulator because of its high molecular density. To get the most out of Argon ensure that the suit is fully flooded with it before you enter the water. By purging and inflating your suit several times ensures a good distribution of argon in your suit.

Note:It is better to purge and inflator your suit under water to reduce the chance of a first stage free flow or inflator freeze up.  See Inflators below

Some industrious divers use electric underwear or put chemical heat packs inside their suits.  However, I have never tried this so I will not comment.

Never use Helium in any inflation gas, especially ice diving, its low density guarantees it is a bad insulator and will cause the body to loose heat more rapidly.


Icy Manifold

Cold water regulators need to be environmentally sealed so no external water can not enter the first stage, however, this alone may not be enough. As a diver inhales as air rushes from the tank because of a drop in the first/second stage pressures, causes a refrigeration effect and an instant drop in internal temperature. Any residual moisture, from condensation or gas humidity, will instantly freeze on the internal parts the regulator if the temperature drops below freezing.   This refrigeration effect can be observed on the outside of the primary first stage because it is usually coved in a thick layer of ice after being used in zero degree water.

The best way to reduce the chance of free flow is to reduce the Intermediate Pressure of the regulator, reducing the refrigeration effect. At the same time it is worth while to slightly increase the cracking pressure of the second stage and turn down “Venturi Assist” or other performance features. You don’t want to feel like you are breathing through a straw, but a slight increase in breathing resistance is acceptable for cold water. I dropped the IP of my regulators back to 125psi and have not seen any problems.

Another common practice is to avoid breathing a regulator or cranking on an inflator before the dive begins. Many ice divers will not even pressurize their system until standing at mouth of the entrance. The air temperature is usually much colder then the water so the likelihood of freeze ups is greater above the water then beneath it.The Buoyancy Compensator is inflated by mouth and the suit should be inflated only after under water.

Note:All regulators taken on an ice dive need to be environmentally sealed and have reduced IP’s.


Many so-called technical BC/dry suit manufacturers often put high performance inflators on their products and market it as a big advantage. There is no advantage in this for an ice diver and may actually be more dangerous. Inflation can put far more demand on a regulator then normal breathing, increasing the risk of free flow, and the inflator mechanism itself can freeze as easily as any first stage.  

A runaway inflator is the most dangerous situation in ice diving and needs to be dealt with immediately. The best way is to disconnect the hose, but not always possible because of ice build up or cold hands, the only other option is to shut down the inflation post. Then there is the cascade of problems that can follow, losing control of ones buoyancy, rocketing for the ceiling, being knocked unconscious by hitting your head on the ice, regulator free flow, loss of gas, separation from your buddies, loosing the line, etc, etc.

No inflator will completely remove the risk of freeze up, but like regulators, a low flow or low performance inflator substantially reduces the risk.  If it does freeze the rate of inflation will be slightly slower buying the diver a little more time to deal with the problem. 

The way a diver uses an inflator can also reduce the risk of a freeze up. I use inflators very sparingly and in small bursts when ice diving.  I also time my inflation between breaths so to reduce demand on my first stage.

Dry Gloves

Dry gloves, when used properly, have many advantages in ice diving.  Keeping fingers separated from the numbing effects of cold water increases dexterity and sensitivity over long exposures. When hands are allowed to loose sufficient amounts of heat they tend to stiffen loose strength and have a reduced sense of touch.   This can make simple tasks exceedingly difficult and exacerbate potentially dangerous situations. In the event of a free flow it usually takes a reasonable bit of hand strength to completely shutdown a tank valve. Sharing air or using reels usually involve a good sense of touch and dexterity.

Dry gloves need to adjust to ambient pressure changes for optimum heat retention and mobility. Gloves that attach directly to the suit without a wrist seal work very well but are prone to catastrophic suit floods should they be punctured, a huge disadvantage for ice diving.  A preferred type of glove attaches a cuff ring to a suit while preserving the wrist seal, in the event of a glove puncture only the hand will be compromised. However, for this glove to work properly a wick is needed in under the wrist seal to allow gas to trickle between the arm and the glove, usually a small piece of string or clothe material will work. The only disadvantage to this is if water enters the glove it will find its way into the arm of the suit, but the rate of flooding should be relatively slow and provide enough time to remove the wick and abort the dive safely.

For short exposures a diver can get away with 3 fingered mitts providing they are a good fit and have a tight wrist seal, but nothing can compare to dry gloves in cold water. Divers new to dry gloves will require some extra practice to get use to them, but once mastered they will be a much appreciated piece of kit.


At 0c/32F up to 30% of body heat can be lost through the head, so a diver needs to have a properly fitting high insulating hood to reduce this loss. A dry hood is the optimum choice, but like dry gloves, does require practice.  Also the hood needs to be correctly fitted or it will leak more often than keep you dry. My experience with dry hoods has not been favourable and I usually opt for a proper fitting wet hood, which gives me more than adequate protection for up to an hour in zero degree water.  However, for extremely long exposures a dry hood may be the only option.

Full Face Masks

Full face masks do keep the face completely dry and warm and provide for additional communication, however, they do have one distinct disadvantage. In order to share air they need to be either completely removed, blinding the diver, or special second stages/hoses are needed to connect to the mask. This makes air sharing a complex task for an already stressed diver. Any divers using these should be well versed in emergency procedures and have adequate practice. Again for extremely long exposures there may be no other options, but currently the length of my ice dives has not warranted the use of a FFM.


The ice diver will always have the addition of a reel or guide line which makes navigation a non issue; however, in the event of a lost line a compass may be the only way to return to the entry point or reacquire the line. Before a dive it is worth while to take a compass bearing on the surface and to note any change in direction when under water.

Compasses are liquid filled and surrounded by plastics that will be affected by cold.  On really cold days I have seen my compass freeze solid and not work again until after it has been warmed up. They should have a high cold rating and be kept as warm as possible before a dive 

Reels and spools

Reeling out under ice

Each buddy team should have a primary reel with an adequate amount of line to do the dive.  Optionally each diver may carry a primary reel which can be used to continue the dive after the current primary reel is exhausted. Each buddy should also carry a gap reel/spool to tie onto the primary line in order to branch off if necessary. The gap reel becomes particularly important when needing to leave the primary line; any attempt to deviate from the primary should first be followed by a gap reel tie in 

Note: The event of a lost line in a frozen body of water may present even more difficulty then in a cave environment. A diver may not have access to a tie in point from which to start a sweep also with out any walls a diver can end up a large distance away from the line. Again a compass may be your only source of direction


Even though diffused light can penetrate the ice layer and illuminate the aquatic realm very well, ice divers should always take lights with them, to allow for buddy signaling and help illuminate the guide line. Also, it is standard cave diving procedure for divers to carry two backup lights, a practice I wholly support for ice diving.

The most important feature of a primary light is to have a bright focused penetrating beam allowing light to travel over longer distances or to punch through a low visibility situation. Signaling a buddy and finding a lost line or landmark suddenly becomes much easier with a bright focused beam light.

The primary light must also have a long burn time in cold water and be able to last the entire length of the dive, canister lights make excellent primaries. Backup lights need not be as big/powerful as the primary but adhere to similar principles, focused beam and reasonable burn times.

Gas Management

Applicable to any overhead environment, good gas management skills are a must. An ice diver must have enough gas to see themselves and their buddy safely back to the entrance in the event of an emergency at longest point away from the entrance. Divers must consider currents, obstacles and other potential hazards of the site that may delay a quick retreat. I use a very simple gas management technique to accomplish this.

Ice divers should wear a twin tank configuration on their back and carry a stage bottle of same/similar size to one of the back gas bottles. The back gas supply should be treated as a reserve, only used when absolutely necessary, and the stage used to perform the dive. The idea being a dive should be planned so that each diver returns with ~500psi/40bar in their stage bottle and completely full back gas tanks, meaning the turn point of the dive is when the stage reaches the half full mark (plus 500psi/40bar). There are several advantages to this method.

First the diver has a completely separate redundant stage bottle for which to do the dive. Should any thing happen to this bottle it can easily be shutdown and the diver resort to the back gas.  Secondly divers can tell how much gas they have left and easily judge the turn around point of the dive. Thirdly the volume of gas in the back gas reserve is twice the amount used to do the entire dive, which in the worst case, an air sharing situation at the half way point of the dive, would be able to get two divers safely back to the entrance. Fourth, if time was of the essence, like in a leak situation, the stages can be ditched in favour of a faster stream lined diver and a second dive planed to retrieved the bottles afterwards.

Miscellaneous tools and procedures

Ice Diving equipment

Ice divers require additional tools not common in cave or wreck diving. A portable camping stove for warm water and hot chocolate, a chain saw capable of cutting the ice, an ice auger to drill holes and a grapple attached to a length of rope is needed to help pull blocks of ice out of the hole. The grapple can be a hook or something as simple as a piece of steel pipe or angle iron. A shovel is also handy to clean away the ice and to make sky lights for light penetration, not to mention if your truck gets stuck in the snow 

To make a diving entrance the diver must clean away any snow from where the cut will be made. The shape of a 2x2x2 meter triangle etched into the ice. The triangle needs to be divided into manageable size blocks before the ice is cut, about 0.5m x 0.5m in size, with an auger hole in the center each block. When cutting the entrance it is best to start in the middle and work toward the outside. When the blocks are cut free and floating the grapple is lowered into the center auger hole and the blocks pulled clear of the hole. The blocks maybe very heavy so it could take three or more strong people to do this, another option is to use a vehicle to pull out the blocks.  

Note:Never push the blocks in under the lip of the hole, for two main reasons. Natural currents or diver error could cause the blocks to shift back into the exit.  After diving is completed the hole needs to be covered in again so children, animals or snowmobiles do not accidentally fall in. The ice blocks can be used to bury the hole afterwards.

Once diving begins the entrance needs to have a tender, somebody who is prepared top stay top side to ensure that the hole does not freeze over or blocked by shifting ice.  Logistically it is good to have two buddy teams; one team enters first and the other guards, then vice versa.

Guide lines and reels need to be connected to some surface feature that is guaranteed to be immovable. A vehicle, tree or dock will work well, however, if too far away an Ice Anchor can be used. An anchor can be purchased in mountain equipment and hiking stores and provide an excellent alternative to natural features. 

For extra safety divers can sprinkle some grit, like kitty litter, around the entrance to prevent slipping. If diving for an extended period of time divers can erect a small tent or shelter around the entrance to help break the wind and keep snow and keep out other debris. The tent can also be heated (to a certain extent) using portable propane heaters and such. In areas frequented by ice fishermen, ice fishing huts can be utilized as a changing stations and shelter for long periods of ice diving.

To get your gear out on the ice a toboggan or sled can be towed by a diver on foot. For traveling long distances, snowmobiles or 4 wheel ATVs can be attached to bigger sleds, called “Komatiks”, used to pull the gear. Realistically the diver may borrow techniques from many winter disciplines to help improve the ice diving experience.

Like any extreme activity, ice diving needs to approached slowly, and experience gained in careful progression.  Divers have to expect it will put more stress on their bodies and gear then any other form of diving, to the point that they can expect something to go wrong far more frequently. Divers have to weigh the risks and rewards, but ultimately the experience of ice diving will make them much more confident and comfortable underwater. When done properly it will mold you and your buddies into a dive team capable of handling just about anything the aquatic realm can dream up.

Ice Diving (Third Addition)
Anthony C. Ferguson
Published: ACUC International 1996