From Washington State Parks Boating Program:
Hypothermia is a serious threat to Northwest boaters, and it takes the lives of several Washingtonians every year. Our marine waters and most of the state's lakes and streams remain cold throughout the year, so hypothermia is a danger that knows no season. A boater who ends up in the water may begin falling victim to hypothermia in a matter of only a few minutes, so quick action is often the key to survival. Understanding and avoiding hypothermia can mean the difference between being alive or dead when help arrives.
What is hypothermia? Hypothermia is subnormal temperature within the central body. When a person is immersed in cold water, the skin and nearby tissues cool very fast. However, it may take 10 to 15 minutes before the temperature of the heart and brain start to drop.
When the core temperature drops below 90 degrees serious complications begin to develop. Death may occur at about 80 degrees, however, a person may drown at a higher temperature due to loss of consciousness or inability to use the arms and legs.
How can I avoid hypothermia? Because most boaters who die in water-related accidents had no intention of going into the water, the obvious answer is to avoid those behaviors that cause accidental immersion:
* Do not stand or move around in a small boat
* Do not overload your boat or distribute the load unevenly
* Do not decelerate suddenly, allowing the stern wake to overtake and swamp the boat by washing over the transform
* Always wear a lifejacket on the water