General Cold-Water Diving
The term 'cold-water diving' can be interpreted quite openly, the term generally means diving in the latitudes of the world where the water temperature is sufficiently cold to necessitate the wearing of effective thermal protection. This statement covers most of the globe, and certainly includes the diving areas around north-west Europe, parts of North America and Eurasia. Sub-tropical areas are less likely to be 'cold-water diving' zones, typically they are considered 'warm-water' for summer yet 'cool-water' for the rest of the year. Having said some think it wise to consider 'cool-water' areas as 'cold-water diving' for the safety purposes.
For this page of lore, diving in temperatures lower than 10 degrees celsius can be considered relevant. In Britain and central Europe these are the winter diving conditions in the sea. If we go to higher latitudes, the cold conditions are likely to last for longer periods of the year. It is worth knowing that even in the height of summer fresh water lakes, especially those at high altitude, can remain at a low temperature.
The human body temperature is naturally suited to dry-land and when exposed to cold water body temperature can drop dramatically. How much its drops will depend on how much thermal protection protects your body. Even when a diver has left the water his body temperature can continue to drop until the body can be fully re-warmed. This fall can drop even more than when the dive was in the water, and, if not dealt with swiftly, hypothermia can set in. Thus, the diver is at greatest risk from the time he finishes his dive and leaves the water until he has changed back into warm clothes again. Long periods sitting in open boats in a cold breeze can only exacerbate the situation.
The situation is made worse by repeat dives, especially if the diver has not been able to fully rewarm between dives. The rate of temperature is likely to be higher on a second or subsequent dive, and again the amount by which the body temperature drops will depend on the water temperature, dive time , surface interval, surface chilling factors and body insulation.
A diver in these circumstances is not always the best judge of just how cold he is becoming. This indicates the need, in these situations, for rigorous dive marshalling in order to ensure that divers do not accidentally overexpose themselves in or out of the water.
In the water the body must,therefore, be protected from cold temperatures. The choice is between a wetsuit and a drysuit. A good-fitting wetsuit can be quite adequate for even very cold conditions. Divers in Antarctica regularly dive using 10mm thick neoprene semi-dry wetsuits. However, for general cold-water diving, including the seemingly inevitable messing about on the surface that this entails, many sport divers choose a drysuit. The type of drysuit is not too important, provided that the diver wearing adequate thermal insulation of one form or another.
Once out of the water the situation id quite different. The properties that make wetsuits work under the water to keep the diver warm act against him on the surface. The thin layer of water trapped between the suit and the body soon chills and conducts heat away from the body. The prime requirement for a wetsuited diver before, and especially after a dive is to wear a windproof.
The drysuited diver has a similar problem. Partial inflation of the drysuit with air while in a boat can help the situation, since this serves as an extra layer of insulation between the suit and the body, thereby reducing the chilling effect.
The colder the water and air temperatures, the stronger the chilling effect of the wind and the more insulation the body needs. The extremities of the body are great conductors of hear. Divers should protect exposed heads and hands and woolen garments such as balaclavas and mittens are most effective. Full facial protection may be necessary on occasions and neoprene face protectors have been developed to meet this need.
Cold Water Diving | Ice Diving