Five years ago, expert sea diver and Naval Captain Jonas Taylor encountered an unknown danger in the unexplored recesses of the Mariana Trench that forced him to abort his mission and abandon half his crew. When a submersible lies sunk and disabled at the bottom of the ocean, carrying his ex-wife among the team onboard, Jonas must confront his fears and risk his own life to help rescue the trapped crew and face the possibility that the Carcharodon Megalodon may still be alive.