Humanoids from the Deep, also known as Monster in Europe and Japan, is a 1980 American science fiction monster movie starring Doug McClure, Ann Turkel, and Vic Morrow. Roger Corman served as the films uncredited executive producer and his company New World Pictures distributed it. Humanoids from the Deep was directed by Barbara Peeters also called Barbara Peters and its musical score was composed by James Horner.
The following day, teenagers Jerry Potter Meegan King and Peggy Larson Lynn Schiller go for a swim at the beach. Jerry is abruptly pulled under the water. Peggy believes it is a prank until she discovers his mutilated corpse. Peggy screams and tries to reach the beach but a monstrous figure attacks her and drags onto the sand. The humanoid creature tears off her swimsuit and rapes her.That night, two more teenagers are camping on the same beach. Billy David Strassman is about to have sex with his girlfriend, Becky Lisa Glaser when another humanoid monster claws its way inside, kills him and chases Becky onto the beach. She outruns her assailant but then runs into the arms of yet another monster, which throws her to the sand and rapes her. More attacks follow not all of them successful, but few witnesses survive to tell the public about the incidents only Peggy is found alive, though severely traumatized. Jims brother is also attacked, prompting Jim to take a personal interest in the matter. ........
Source: Wikipedia