Ralph Meeker stars as John Dexter, a wealthy adventurer/hunter who is on a fishing expedition in a Latin American country with his secretary(played by Janet Blair) and other members when they stumble upon a humanoid-shaped sea creature that they manage to capture. The creature has sonic abilities to use as a self defense weapon, or to communicate with others of their kind, as they will all discover when a rescue mission is mounted... Henry Silva co-stars as General Mercurio, the country's dictator. Good premise here, and the creature costumes really are not that bad at all, though this is marred by the dull, clichéd human characters. Still, a guilty pleasure.