Blood Tide

Neil and Sherry Grice, a young American couple, are visiting Greece in search of Neil's missing sister, Madeline, an artist who traveled to a remote island off the coast shortly before her disappearance. While touring the island, the couple are met by Nereus, the elderly mayor, who is initially hostile toward Neil. Frye, a middle-aged treasure hunter, is found with Madeline, and Neil and Sherry soon discover that an ancient monster has been released, forcing the villagers to sacrifice virgins to appease it.