I thought folks here would appreciate this article I put together. I sourced a lot of information from 'Dr. Popsicle' who specializes in cold water immersion research.

Here's the first few paragraphs,

Ocean water and most rivers and lakes are now cold enough to induce hypothermia or incapacitation in about 10 minutes.
Dr. Gordon Giesbrecht (aka Dr. Popsicle) from University of Manitoba has been conducting improtant research into the effects of cold water immersion on the human body. His excellent website ColdWaterBootCamp.com is full of information that most people living in cold climates should know.

From the Cold Water Boot Camp Cold Facts page;
In 2004, 410 people drowned in Canada, 130 were boating.
- life jackets save lives in cold water
-43% of the people were less than 2 metres away from shore or safety
-66% of the people were less than 15 metres away from shore or safety
From the Cold Water Boot Camp Preventation page;
- in addition to having proper flotation,…drawing your legs close to your chest and wrapping your arms around them in a tuck position will help conserve body heat.
- if you’re in a group, huddling together as close as possible will also help conserve body heat.

Treatment for mild hypothermia
-If there is no way to get to a medical facility within 30 minutes, a mildly hypothermic person should be rewarmed as follows. Shivering is a very effective process especially when well insulated. Shivering should be fueled by calorie replacement with fluids containing sugars. The sugar content is actually more important than the heat in warm liquids. Make sure that the person is capable of ingesting liquids without aspirating. Alcohol and tobacco use should not be permitted because they constrict blood flow.
-External heat can be applied to high heat transfer areas such as the underarms and sides of the chest. Active heating of the skin is beneficial as it increases comfort, preserves energy stores and reduces cardiovascular stress
-Light exercise such as walking produces heat but should only be attempted after a mildly hypothermic person is dry, has had calorie replacement and has been stable for at least 30 minutes. A warm shower or bath may be tolerated by an individual that is alert and mobile. However, this could be fatal to a moderate to severely hypothermic person and should be avoided in this case.
....

If you are interested in the complete article please check it out here;

Cold Water Immersion Safety 101