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.
As Abraham Lincoln labors over the Gettysburg address, the importance of which he is fully aware, he learns that a menace from his past has returned, threatening to tear the already fractured nation to pieces. He must journey behind enemy lines to face an foe far more fearsome than the Confederate army: the walking dead.