Seven years after he survived the monster apocalypse, lovably hapless Joel leaves his cozy underground bunker behind on a quest to reunite with his ex.

An adventure-loving couple convince their friends to explore a remote, uncharted cave system in the forests of Northern Australia. With a tropical storm approaching, they abseil into the mouth of the cave, but when the caves start to flood, tensions rise as oxygen levels fall and the friends find themselves trapped. Unknown to them, the storm has also brought in a pack of dangerous and hungry crocodiles.