When a massive creature attacks a submersible, the crew becomes trapped at the bottom of the Pacific's deepest trench. To save them from the clutches of the Megalodon - a prehistoric 75-foot shark once believed to be extinct - a visionary oceanographer recruits expert rescue diver Jonas Taylor. Teamed with the oceanographer's daughter, Suyin, Taylor must try to outwit the greatest predator alive... a killer he's faced once before.