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. Two sisters diving in a ruined underwater city quickly learn they've entered the territory of the deadliest shark species in the claustrophobic labyrinth of submerged caves.