Immersion in cold water is a hazard for anyone participating in activities in the oceans, lakes and streams of all but the tropical regions of the world. The U.S. Coast Guard defines cold water as being below 70 degrees Fahrenheit. Hypothermia will eventually result from immersion in water below this temperature. The risk of immersion hypothermia in North America is nearly universal during most the year.
Cold-water immersion is associated with two potential medical emergencies: drowning and hypothermia. Numerous case histories and statistical evidence document the importance of cold-water immersion as a cause of drowning and hypothermia. Perhaps the most famous occurrence of cold-water immersion was the sinking of the Titanic on April 14, 1912. After striking an iceberg, the ship sank in calm seas. Of the 2,201 people on board, only 712 were rescued, all from the ship's lifeboats. The remaining 1,489 people died in the water, despite the arrival of a rescue vehicle within two hours. Nearly all of these people were wearing "life preservers," yet the cause of death was officially listed as drowning. More likely, the cause of death was immersion hypothermia.World War II, especially in the North Pacific and North Atlantic oceans, provides many examples of accidental immersion in cold water. Recreational activities are a major source of immersion incidents. In a recent year, the state of Alaska had 253 deaths from accidental causes. Of these, 132 involved water-related deaths from either drowning or hypothermia.
Cold-water survival
For immersion hypothermia, the most important factors affecting cooling rates in cold water are:
- Water temperature (colder is more dangerous).
- Survivor's percentage of body fat (more fat increases survival chance).
- Type of protective clothing worn by the survivor (wet suits protect).
- Survivor's behavior in the water (little motion preserves energy).
- State of the water (i.e., waves splashing over the head causes heat loss).
- Amount of a survivor's body immersed in the water (more water contact increases chances of hypothermia).
Those with high amounts of body fat cool more slowly than do those who are skinnier. Also those with large body size have slower cooling rates than do smaller persons.
In cold water, hypothermia develops in a short time in unprotected adults. If the water is not only cold, but moving quickly, hypothermia may develop at an incredibly rapid rate. A child's temperature drops even more quickly because of the relatively large surface-area-to-mass ratio and the lack of subcutaneous fatty insulation.
Maximum heat loss occurs from the head, the neck, the sides of the chest and the groin. Swimming and other motion enhances this loss, increasing the risks of hypothermia. Since the cooling process is enhanced by movement, the better swimmers often die first, since they are more likely to try to tread water rather than just float. Likewise "drownproofing," a technique of bobbing in the water, will markedly increase the heat loss as water circulates about the head. Based upon studies, a heat escape lessening posture (HELP position) was devised in which the victim draws the knees up close to the chest, presses the arms to the sides, and remains as quiet as possible. For three or more persons, huddling quietly and closely together will decrease the loss from the groin and front.
The U.S. Coast Guard and other rescue organizations recommend that a survivor get as much of his body out of the water as possible in order to minimize cooling rate and maximize survival time. This means even if exposure to cold wind and spray results. A widespread misunderstanding of the concept of "windchill' often causes many to conclude that survivors have higher heat losses if they are exposed to wind, especially if they are wet, than if they are immersed in water. During recreational activities at the beach, lake or swimming pool, some people have experienced feeling colder after leaving the water than they do while swimming. This reinforces the misunderstanding. This has sometimes led accident victims to abandon a safe position atop a capsized vessel and to reenter the water, usually with tragic results.
The history of mankind's association with cold water provides abundant examples of the effects of accidental cold-water immersion. For example, several years ago, two Utah County physicians who were duck hunting on Utah Lake had their boat capsize. One survived and one didn't. Cold-water immersions are not confined only to the cold waters of the oceans - virtually all North American waters can produce hypothermia. This includes all lakes and rivers in the Intermountain West.