'Deadliest Catch' Captain Bill Wichrowski -- Masturbation Is a High Seas Sedative

"Wild" Bill Wichrowski has the cure for insomnia in the open waters ... a little self-gratification.

It's unclear why our photog and the "Deadliest Catch" captain were obsessed with talking about masturbation ... but they had quite the revealing chat about "relieving yourself" on a boat.

Wichrowski went on about the preferred locations for a little one-on-one, as well as how a quick session can help the guys fall asleep on the high sea.