Four teenage girls go on a diving adventure to explore a submerged Mayan city. Once inside, their rush of excitement turns into a jolt of terror as they discover the sunken ruins are a hunting ground for deadly great white sharks. With their air supply steadily dwindling, the friends must navigate the underwater labyrinth of claustrophobic caves and eerie tunnels in search of a way out of their watery hell.

Durante una inmersión, dos hermanas de vacaciones en México se quedan atrapadas en una jaula de avistamiento de tiburones, con el oxígeno agotándose y rodeadas de peligrosos tiburones blancos. Sin ayuda en la superficie, sin ayuda bajo la superficie.