In the tradition of Shadow Divers, this is the gripping true account of the search for German U-boat U-550, the last unfound, diveable wreck of a U-boat off the United States coast, and the battle in which it was sunk. On April 16, 1944, the SS Pan Pennsylvania was torpedoed and sunk by the German submarine U-550 off the coast of Nantucket, Massachusetts. In return the sub was driven to the surface with depth charges, and then sent to the bottom of the ocean by three destroyer escorts that were guarding the naval convoy. For more than sixty years the location of the U-boat’s wreck eluded divers. In 2012, a team found it—the last undiscovered U-boat in dive-able waters off the Eastern Seaboard of the United States, more than three hundred feet below the surface. This is the story of their twenty-year quest to find this "Holy Grail" of deep-sea diving and their tenacious efforts to dive on this treacherous wreck—and of the stunning clash at sea that sealed its doom and brought the Battle of the Atlantic to America’s doorstep.

In cold, murky water, working by touch alone, they can defuse a mine powerful enough to sink a battleship. Under the burning Afghan sun, they can dismantle a Taliban roadside bomb. Welcome to the world of the Royal Australian Navy clearance divers. Bomb and mine disposal is but one of their roles. As covert swimmers they can infiltrate enemy waters. As boarding parties they are on the anti-piracy frontline. As counterterrorist special forces they are on call 24/7. They are simply one of the best diving units in the military world. Their story goes back to the Second World War, when Hitler's secret weapon - the magnetic mine - had Britain on her knees. Four extraordinary Aussies were among the brave naval volunteers who tackled Nazi mines on land and under water. The men who followed their path share the same brand of courage. From the rivers of Vietnam to the deserts of Afghanistan, navy divers have excelled under the most dire pressure, yet we know very little of their heroic deeds. Their incredible story has remained behind closed doors. Until now . . .