Raise the Nautilus

A tech billionaire discovers a zero-sum energy device from wreckage located at the bottom of the world's deepest oceanic trench .Deeper than Mount Everest is tall. The United States Navy sends for Mallory Capehart, their best salvage officer... Commander Mallory Capehart USN. She is haunted by memories of a past disaster that killed everyone on her dive team and suffers from acute PTSD. Her mission? To raise and recover the wreck of a legendary vessel.
Mallory accepts the top-secret assignment to do the impossible and no one knows whether she'll succeed. Adding to her problems are the Chinese and Russians who also want the zero-sum energy device. And Mallory isn't quite sure who's side some of her teammates are on.