Loch and his sister are with their father on a scientific expedition when suddenly a hideous water beast explodes out of the water, and a photographer, hoping to get the picture of a lifetime, gets devoured instead. The plesiosaurs terrorize the secluded lake community, but Loch encounters a baby plesiosaur and realizes that the monsters only attack when threatened. So he risks his life - and the lives of his family and friends - to save the prehistoric creatures from destruction.