A professional surfer competing in a contest at San Francisco's Ocean Beach left the water in the middle of a heat after saying he saw a large shark.
Surfer Dusty Payne of Hawaii left the surf on Tuesday while competing against another surfer, saying he saw a large shark just outside the lineup.
Payne said he has seen many dolphins before, and that he was sure it was not a dolphin. He called it the "biggest fin I've ever seen in my life coming straight at me."
The sighting follows an attack by a 9-foot shark on a surfer Saturday at Marina State Beach in Monterey County, about 100 miles south of San Francisco.
Eric Tarantino suffered injuries to his neck and arm, but was released Monday from the hospital.
The contest was continuing after the sighting.