Troglodyte

Following a string of accidents, fisherman Will and his crew are becoming concerned about the disappearing fish population in the area, which puzzles Arden, the local biologist. When a couple of locals are attacked and found ripped to pieces, his story about a vicious sea creature being responsible is laughed off in favor of more traditional suspects. More are attacked, and the creature is positively identified as a carnivorous reptilian sea creature that lived on the ocean bottom... (imdb)