Grace, her boyfriend Adam, and younger sister Lee decide to take a river tour while holidaying in Northern Australia. As they drift into a mangrove swamp their boat is suddenly capsized and Jim, their guide, disappears. Realising they've been attacked by a crocodile, Adam drags Grace to the safety of a tree while Lee clings to the top of the overturned boat. Adam and Grace frantically try and manoeuvre Lee and the boat to the tree but it is firmly stuck. Stranded in the flooded mangrove swamp, the three holiday-makers must work out what to do to survive.

What you can't see, can hurt you...