John Dexter is a wealthy adventurer who sets out with a group of scientists to find new marine life in the oceans around a Banana Republic. They soon spot a mysterious fish creature that is also a local legend. Villagers believe the fish creature is a God. Dexter and his chief marine biologist, Tom Evans, dive and spear the creature. However, Evans panics and swims away, leaving Dexter to fight the creature on his own. Dexter subdues the creature and they bring it to the surface.
News of the capture reaches the ears of the country's Socialist dictator, General Juan Mercurio. He comes in with propaganda photographers and poses triumphantly next to the creature. Soon, Mercurio realizes the creature would be the perfect display for his failing tourist attraction.
Dexter's girlfriend, Lynn Arthur, is a reporter who once worked for a newspaper Dexter purchased and shut down. She is in love with him, but can't break through his impenetrable veneer.
Later, the specimen unfreezes and has used some amazing healing power to heal the wound. It escapes momentarily, but is recaptured by village men. Knowing a live specimen would enhance his reputation, General Mercurio threatens to kill any man who touches the creature.
Dexter fights off the lone guard and tries to leave the country with the creature, but dozens of fish creatures emerge from the waters to save their companion. Dexter tries to mow them down with a machine gun but the fish continue, due to remarkable healing powers. He falls back, afraid for the first time in his life.
The creatures disappear back into the water and Dexter seems to have had a life altering experience. The creatures use their ultrasonic powers on a large dam, which floods the country and kills General Mercurio. Dexter and Lynn are seen helping the villagers in the final scene.