一项由中国主导的国际科研项目，正在马里亚纳海沟深处进行时，遭遇未知生物攻击，科研人员被困海底。前美国海军陆战队深海潜水专家乔纳斯·泰勒受命前往营救，再度遭遇数年前曾经在深海给自己留下终身难以磨灭记忆的史前生物巨齿鲨。乔纳斯联手科研项目中的中国女科学家张苏茵成功营救了被困人员，但营救行动却意外造成了巨齿鲨逃离深海。当史前巨兽重返浅海，人类将为自己对大自然的贪婪付出惨重的代价......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. Though the tragic incident earned him a dishonorable discharge, what ultimately cost him his career, his marriage and any semblance of honor was his unsupported and incredulous claims of what caused it - an attack on his vessel by a mammoth, 70-foot sea creature, believed to be extinct for more than a million years. But when a submersible lies sunk and disabled at the bottom of the ocean - carrying his ex-wife among the team onboard - he is the one who gets the call. Whether a shot at redemption or a suicide mission, Jonas must confront his fears and risk his own life and the lives of everyone trapped below on a single question: Could the Carcharodon Megalodon - the largest marine predator that ever existed - still be alive ... and on the hunt?