The Beach Girls and the Monster (1965)

Director: Jon Hall
Cast: Arnold Lessing, Carolyn Williamson, Elaine DuPont, Gloria Neil, Jon Hall, Kal Roberts, Read Morgan, Sue Casey

Synopsis:

A young girl is killed at the beach in Malibu. Professor Otto Lindsay suspects that it is some form of mutated fish. However, his son Richard, who was a good friend of the girl, thinks that it is a madman who has a grudge against Richard and his friends. Soon the list of victims grows.