With all natural animal and plant life either dead or too radioactive to eat, the survivors of a global catastrophe are forced to turn to the seas for their sustenance, hunting the mutated beasts which live in its black depths.

Ethan, a wasteland survivor, is put to work and sent out on a hunting trip to capture and kill one of the sea dwelling beasts that are the stuff of legend.

However, when they spot something impossibly large and give chase. Ethan is pulled into a terrifying battle between man and monster in the cold desolate ocean, where he realises that not only are the stories of the leviathans true, but they are far worse than anyone could ever imagine.