A 61-year-old FedEx pilot stranded in the Gulf of Mexico without a life jacket, tread water for 20 hours in a desperate bid to stay alive. William Durden fell off his fishing boat Wednesday, June 1, 2016, while fishing alone. He somehow was able to tread water off the coast of Florida for all those hours while awaiting rescue. Durden credits his Navy training for knowing what to do. "They teach you how to drown proof yourself, what position you need to be to stay above the water instead of below it," he said.

20-HOUR SWIM IN THE GULF OF MEXICO

An MH-60 Jayhawk helicopter crew from Air Station Clearwater, Florida, rescues a man from the water 18 miles west of the Homosassa River entrance in Florida, Thursday, June 2, 2016. An HC-130 Hercules fixed-wing aircrew from the air station located William Durden, 64, from Reno, Nevada, after he fell off his boat and treaded water for more than 20 hours. (U.S. Coast Guard video)

It was June 1, 2016, the first day of Grouper season, and FedEx Pilot Bill Durden was out fishing. He had quickly landed two large Groupers and was enjoying a beautiful day 25 miles from shore in the Gulf of Mexico. Moments later he would find himself in the water, without a life vest, watching his boat head into the horizon. This was the beginning of his incredible journey 20 hours alone at sea.