A small, secluded island in the Caribbean suddenly finds itself terrorized by a deadly predator from the planet's distant past when deep sea divers accidentally awaken an ancient evil. Jackson Slate and his team of underwater cave explorers unearth much more than long-lost Mayan treasure while plumbing the depths of a world famous blue hole. They disturb a creature that's been hibernating for over 100,000 years -- POSEIDON REX -- a rampaging behemoth of death and destruction not only at sea but also on land. As a devastating tropical storm descends upon the island, Jackson and the surviving members of the island community must try to stay alive long enough for help to arrive. When they realize the military intends to bomb the creature and the island into the next century, they realize their only hope is to make it to the mainland... even if that means going back in the water.