Marine biologist Jack Ellway and his son Brandon are drawn to the Polynesian island of Malau to study the effects of recent seismic activity on the area's marine life. They soon become caught up in the investigation of a series of recent drownings. As Jack explores the surrounding ocean for a mysterious marine creature, Brandon discovers and befriends the creature's baby sibling, a three-foot long amphibian that is able to leave the ocean and walk on land. As more dangerous and giant creatures come onto the island, the military takes action. Jack must risk everything to save the creatures, the island and his son.