In the fall of 1991, in the frigid Atlantic waters sixty miles off the coast of New Jersey, weekend scuba divers John Chatterton and Richie Kohler made a startling discovery under decades of accumulated sediment: a World War II German U-boat, its interior a maze of twisted metal and human bones. Equally astonishing: All the official records agreed that there simply could not be a sunken U-boat at that location.Over the next six years, an elite team of divers embarked on a quest to solve the mystery. Some of them would not live to see its end. Chatterton and Kohler, at first bitter rivals, were drawn into a deep bond of friendship. As the men's marriages frayed under the pressure of a shared obsession, their dives grew more daring, and each realized that he was hunting for more than the identities of a lost U-boat and its nameless crew.