Paul O'Leary was about 100 yards offshore when a shark bit into his ankle. He said he never saw the shark and managed to stay calm after realizing he had been bitten but later required 50 stitches to close the wound.

He said he swims at clothing-optional Kehena Beach, which is in a remote area of the Big Island, two or three times a week. Although he was swimming nude, O'Leary said he put his clothes on before emergency responders arrived.

Click here to watch video of an interview with the swimmer on mobile.