From the back cover:

ON THE PLANET EARTH IS A REALM MORE AWESOME THAN OUTER SPACE

Deep in the Caribbean Sea, a U.S. nuclear submarine mysteriously spins out of control. When a U.S. Navy SEAL team and the crew of DEEPCORE -- an underwater oil drilling station -- dive down to investigate, they are trapped at the edge of a vast underwater trench. Now, as the world above stands poised on the brink of nuclear destruction, they prepare to enter....