If memory serves, we have had 5 deaths from hypothermia in SouthWest Florida waters. In one case, two sailors from Marco Island, sailed up to Sanibel on one of those gorgeous February days. And didn't make it back! On the return trip, they got caught by a cold front, were swamped at night, and found dead by the Coast Guard the next day. The boat was fully servicable and intact. They were in the water, tethered to the boat.

Within the last year, a power boat sank and a woman drowned because she could no longer hold on to the large ice chest she and her husband were using as raft.

If the sea water is less than your core body temperature, you are at risk for hypothermia. Conceivably, you could die of hypothermina in a warm bathtub.