Information on how the human body reacts to exposure to cold water:
Cold water robs the body's heat 32 times faster than cold air.
Normal body temperature is 98.6.
Shivering and the sensation of cold can begin when the body temperature lowers to approximately 96.5.
Amnesia can begin to set in at approximately 94, unconsciousness at 86
and death at approximately 79 degrees.
Physical exercise such as swimming causes the body to lose heat at a much faster rate than remaining still in the water. Blood is pumped to the extremities and quickly cooled.
Should you find yourself in the water, avoid panic. Air trapped in clothing can provide buoyancy as long as you remain still in the water. Swimming or treading water will greatly increase heat loss and can shorten survival time by more than 50%.
Expected Survival Time in Cold Water:
— 50-60°: 1-6 hours
— 40-50° F: 1-3 hours
— 32.5-40° F: 30-90 minutes
— Under 32° F: Less than 15-45 minutes
Mild Hypothermia: Core temperature 98.6 - 96 degrees F
Moderate Hypothermia: Core temperature 95 - 93 degrees F
Severe Hypothermia: Core temperature 92 - 86 degrees and below (immediately life threatening)
Source: United States Search and Rescue Task Force.