Devil Monster
"A vivid tale of savage adventure!"
A schooner disappears at sea without a trace. Years later, evidence of possible survivors prompts the mother of the schooner's mate Jose to hire a tuna boat to investigate. They discover the lad living happily on a South Seas island, and, when he refuses to leave with them, they abduct him. However, Jose gets revenge by leading the ship into the lair of a mysterious giant manta ray.
Directors: S. Edwin Graham
Writers: Juan Duval, S. Edwin Graham, Terry Grey, Thelma Brooks, Tom Hubbard
IMDB: tt0127512