Gearing Up for Cold Water Diving

Thermal Protection

While most divers are putting their scuba equipment into winter storage, others are gearing up for a season of cold water diving. It's a great way for you to remain active in the sport throughout the year. But, in order to remain a contented and safe diver, you need to know about thermal protection.

How the Cold Affects You
Being exposed to cold conditions has an effect on your blood's circulation. Usually, blood flow to your skin and appendages is diminished in favor of keeping your vital organs warm. The reduction in circulation happens gradually over the course of a dive or multiple dives. Because of the impaired blood flow to your body's appendages, finger dexterity is reduced. This can lessen your ability to perform certain skills such as mask clearing, and the capabilities to adjust straps and belts or operate snaps and clips.

Moreover, it is thought that the body tissues of the skin and extremities will have a reduced off-gassing due to the decreased blood flow. Thus, you will have a higher risk of decompression illness (DCI).

Also, when your body is cold during a dive, your rate of breathing increases, which means your rate of air consumption increases, too. As a matter of fact, it will almost double. You'll end up using more air from your tanks in less time than if you were doing the same dive under warmer conditions. Furthermore, you'll have to end your dive with more reserve air in your tank. For example: if you normally end a dive with 200 psi of air, you'll need to end with 400 psi. 200 psi might not be enough if you're cold and your air use has increased.

The effects of being cold and minor problems could climax into a real emergency.

How A Wetsuit Works
A wetsuit is the most common item of exposure protection. The purpose of a wetsuit is to insulate your body and minimize heat loss. Wetsuits operate by trapping a layer of water between your skin and the suit. The heat from your body warms up the layer of water, which helps you retain your body's temperature. The thickness and quality of the wetsuit material (usually neoprene) determine the suit's ability to insulate. The thicker the neoprene, the warmer you'll stay. Also, your wetsuit will decrease heat loss by minimizing the water's movement across your skin. This is why the wetsuit's cut, fit, stretch, seals, and fasteners are important.

A dry suit is the next most common item of exposure protection. It works in much the same way as a wetsuit, except that it keeps you dry. A dry suit insulates your body by trapping air between your skin and the suit, instead of water.

As you descend in the water, your wetsuit compresses because of the water's pressure. This compression of the wetsuit reduces your buoyancy and thermal protection. The biggest reduction in your wetsuit's bulk and insulating protection occurs in the first thirty-three feet of water. There is no way to make up for the lost insulation once you're in the water. Compensate before the dive by putting on extra layers of thermal protection to meet the demands of your diving conditions.
Choosing the proper exposure suit is an important part of planning your dive, whether or not you use a wetsuit or dry suit. By logging water temperatures, depths, bottom times, and thermal protection information, you'll put together a statistical reference work for future dive planning.

Five Strategies For Preserving Body Heat:
For a more comfortable and ultimately safer dive follow these tips for conserving body heat.

  1. Stay warm before the dive. Heat loss is gradual and can start long before you get to the dive site.
  2. Stay warm between repetitive dives. Standing around in wet gear between dives can add to your body's deprivation of warmth through evaporative heat loss.
  3. Get warmed up as soon as possible after a dive. You can start on the dive boat by toweling off and getting into dry clothes.
  4. You can develop hypothermia without immediately recognizing it. When choosing your exposure suit, err on the side of thermal protection.
  5. Become an educated consumer. Visit your local dive shop and have them show you the different styles of protective garments and accessories. Don't be afraid to ask questions.

Comfortable Cold Water Weighting

Cold water diving requires more weight than diving in warm water. Even if you don't require any weights when diving in warm water, you will need at least 10 pounds (4 kg) when you wear a thick wetsuit or dry suit for the cold water. When wearing cumbersome exposure protection, a typical diver will go from his or her normal 8-10 pounds (3-4 kg) of weight to 20 or more pounds (9 kg +).
What does water temperatures have to do with the weight increase? Nothing, really. Your buoyancy increases because of the additional exposure protection needed. Dry suits tend to trap air in pockets and thicker wetsuits mean added pounds of lift. Adding lead weights compensates for these changes in buoyancy.

Dispersal of weight is the key to comfortable weighting. A solitary, burdensome weight source, such as a loaded belt, is difficult to handle in and out of the water, Also, some divers find it painful.
Put only a portion of your weight on the belt then arrange the remainder elsewhere. You'll reduce the discomfort and trim your position in the water column at the same time. Wearing all your weight around your waist tends to propel you into a diagonal swimming position, especially when you have air in your BC. You can stay horizontally trim by depositing some of the weight higher on your body. NOTE: For safety purposes, 60 percent of your total weight should be in a single location and detachable using a quick release mechanism.

One of the most favorite devices for weight distribution is the ankle weight. Ankle weights make your feet heavier, thus eliminating your feet from floating up. In addition to, or instead of, strapping on ankle weights, cold water divers place weights on their tanks. You can use a commercially produced tank weight or fashion you own homemade device. Lead can be placed anywhere on the tank.

Ankle weights, tank weights, and pocketed weights will be difficult to ditch in an emergency situation. It's important that these weights make up no more than 40 percent of the total lead worn and are used in combination with a waist belt, weight integrated BC, or weight harness.
A weight integrated BC incorporates weight carrying pouches into the jacket. The pockets are designed so weights can easily be removed and dispose of in an emergency. They are suited for carrying the large amount of lead required for a cold water dive.

A weight harness positions the burden of weight on the diver's shoulders. The device is a strap on harness that has pockets for weights. You can move the pockets around, making it easier for you to adjust your trim.

Finding the proper weight for cold water diving is similar to weighting for any other dive, except the amount of lead needed is greater. Just don't forget; dispersing the load will make you a much more comfortable diver.

Scuba Regulators
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.

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. 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 use.

Life Preserver/ BC

The use of a life preserver / buoyancy compensator 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.

Face Mask
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.

Suit Selection
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 insulation socks under the boots in a wet suit will help keep feet warm.
  • CAUTION: In very cold water, the wet suit is only a marginally effective thermal protective measure, and its use exposes the diver to hypothermia and restricts available bottom time. The use of alternative thermal protective equipment should be considered in these circumstances.

Variable volume dry suits provide superior thermal protection to the scuba diver in the water and on the surface. The level of thermal protection can be varied through careful selection of the type and thickness of long underwear. Dry suit disadvantages are increased swimmer fatigue due to suit bulk, possible malfunction of inlet and exhaust valve, and the need for additional weights for neutral buoyancy. Nevertheless, because of is superior thermal protection, the dry suit is an essential component of extremely cold water diving.

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.