While on vacation on Northern Australia, Gracie, her husband Adam and her younger sister Lee decide to take the Blackwater Barry tour in the swamp for fishing. Their guide Jim uses a small motor boat and takes the tourist along the river to a remote spot. When they stop, they are attacked by a huge crocodile that capsizes their boat and immediately kills Jim. The three survivors climb a tree and when they realize that help would never come to rescue them, they decide to try to find a way out of their sheltered location. However, in the muddy water, their boat is flipped and the crocodile stalks the trio under the water.