Dagon

In this Spanish horror film, a boating accident off the coast of Spain sets off a chain of terrifying events in the decrepit fishing village of Imboca, where people start to disappear and creatures not quite human begin to appear. Paul Marsh, who has had a disturbing dream of encountering a monstrous mermaid with razor-sharp teeth, finds himself pursued by the entire town after he arrives in Imboca with his girlfriend Barbara. As night falls, Paul uncovers the village's dark secret: they worship Dagon, a monstrous god of the sea, and its unholy offspring are on the loose, leading to a nightmare scenario where humans are kidnapped and bred with or sacrificed to this malevolent deity.