One of the biggest weather-related stories today, was two members of a rowing crew at Iowa State dying on a nearby river. Their boat capsized in high winds. The water temperature was 39 degrees. The river, like many bodies of water in our area, were just ice-covered recently.
Hypothermia can happen within minutes of falling into cold water, but the symptoms generally develop gradually. When the water temperature is 40 degrees or below, serious injury can result in as little as a few minutes. Hypothermia is a physical condition that occurs when the body temperature drops off below the normal 98.6° F. Cold water causes hypothermia 25 times faster than cold air. If you are an outdoors person that spends a lot of time near water in the colder months, be careful. Your brain, heart, and lungs are the first to suffer from the cold, slowing down the vital functions. About 600 people in the US die from hypothermia each year. The expected time of survival in cold water depends on many factors such as swimming ability, body size, cold tolerance, shivering response, body fat, alcohol levels, will to live, psychological state, layers of clothing, and flotation devices.
If the temperature of the water is 32.5° F, a person can survive up to 45 minutes, but the body will get exhausted and damaged in less than 15 minutes. The higher the temperature, the more chances you have of surviving. For example, at 60–70° F you can survive in the water from 2 to 40 hours.
If you fall into cold water, your body heat is the essential factor that can help you survive until help arrives. If you have a life vest and the water temperature is 50° F, then if swimming you will have about 2 hours and holding with some kind of support up to 4 hours. Wearing a personal flotation device will increase your chances of survival. Try to keep as many parts of your body out of the water as is practically possible. Never take off your clothes! Remember that you always need to remain as still as possible to conserve energy, unless you see a floating object, another person, or the shore is nearby. In these cases, you would be best to swim and save your life. In any other situation, remain still. Whenever you do your outdoor activities near water, DON’T WEAR COTTON! Wet cotton is heavy and it’s the worst insulator. The outer layers of your clothes should be waterproof. Clothing made of material like Gore-Tex will keep the cold off your body for a while and won’t pull you down.
When is the water warm enough to swim in? According to the National Oceanographic Data Center, 70-78 degrees is where most people feel comfortable swimming. This is relative.