Twins Alena and Tyler Worthy, and their clever terrier Brutus, must try and rescue their friend Xochitl Melendez who has mysteriously disappeared. The twins fear the worst when they go in search of their friend, only to discover several dead hammerhead sharks while diving off the Central American coast around the Cocos Islands. The twins will need every resource at their disposal and every bit of courage as they encounter a series of underwater explosions that lead them to nearby Wafer Bay, a treasure hunter's ship, and an explosive device in need of disarming before further threatening the lives of thousands of marine creatures and delicately preserved, centuries old sea caves.