Arriving by boat at her familys Louisiana lake island cabin, Sara (Sara Paxton) and her friends quickly strip down to their swimsuits for a weekend of fun in the sun. But when star football player Malik (Sinqua Walls) stumbles from the salt-water lake with his arm torn off, the party mood quickly evaporates. Assuming the injury was caused by a freak wake-boarding accident, the group realizes they have to get Malik to a hospital on the other side of the lake, and fast. But as they set out in a tiny speedboat, the college friends discover the lake has been stocked with hundreds of massive, flesh-eating sharks! As they face one grisly death after another, Sara and the others struggle desperately to fend off the sharks, get help and stay alive long enough to reach the safety of dry land.