A group of military researchers (Kristen Stewart, Vincent Cassel, T.J. Miller, Jessica Henwick, Mamoudou Athie) descend to a subterranean laboratory five miles from land and seven miles below the surface of the ocean. They are scheduled to stay there for a month, but when an underwater earthquake shakes their foundation, water begins to pour into their inhabited space.

With the threat of the lab collapsing, the team of researchers must leave the station to travel to safety by walking across the bottom of the ocean. This is when they realize they are not alone: they are being followed and stalked, one-by-one, by a mysterious creature.