The Monster of Piedras Blancas (1959)

A monster that looks like a snarling "Creature from the Black Lagoon" invades a sleepy seaside town. The lighthouse keeper, widowed and estranged from the townfolk, has been secretly leaving food out for the monster for years, unaware of its bloodlust. When the monster's appetite outstrips the keeper's ability to serve it, bloodless decapitated corpses start to appear.