Sea Serpent

The  Sea Serpent is a minor antagonist in the Japanese film King Kong Escapes.

King Kong Escapes
He appears very briefly in the film. After the protagonists attempt to leave Mondo Island, the Sea Serpent attacks their hovercraft. However, King Kong goes into the water and the two monsters begin to fight. The Serpent attempts to constrict Kong, but the gorilla frees himself from his opponent and tosses him back into the water. The Giant Sea Serpent isn't seen again for the rest of the film.