A former Navy pilot who fell from his fishing boat spent 20 hours treading water off the coast of Florida before the Coast Guard rescued him Thursday.

William Durden, 64, was spotted Thursday morning by a MH-60 Jayhawk helicopter crew about 18 miles off the coast of Aripeka, according to the Coast Guard. A video posted by the Coast Guard showed a diver plunge into the waters and lift Durden to safety.

Durden, who is from Reno, Nevada, but has a Florida vacation home, went boating Wednesday. When he didn't return that night, his wife reported him missing, according to NBC affiliate WFLA. His 22-foot boat was found near St. Martins Keys, about 60 miles north of Tampa, early Thursday, but Durden was still missing.

"When you watch your boat motor away you think well I’m just going to do it or I’m going to sit out here and die," he said. Durden chose to fight in the cold waters overnight, and when he saw the rescue helicopter, he started waving his hands furiously.

"They flew by, and I thought they didn’t see me and then a few hundred yards later, they dropped the flare and I was like, ‘Yes. I’m going to live through this thing,'" Durden said.

The 64-year-old credits his Navy training for his survival.