This was when special effects were "special".
There's a creature in the water and he burns his victims. He likes to tip over your boat and give a nice big bear hug.
This is because the poor man in the rubber suit can't do anything else.
There's the scientist who's conducting strange experiments, his daughter who is none the wiser, a couple detectives trying to solve the murders and an envious secretary with a thing for harpoon guns.
This movie ranks up there with the rankest of B movies.