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 on Mexican vacation are trapped in a shark observation cage at the bottom of the ocean, with oxygen running low and great whites circling nearby, they have less than an hour of air left to figure out how to get to the surface.