In the tradition of Shadow Divers, the story of the courageous men who dived on the last sunken U-Boat off the Eastern Seaboard. On April 16, 1944, the tanker SS Pan Pennsylvania was torpedud and sunk by the U-550. In return the sub was sent to the bottom by three destroyer escorts which were guarding the convoy. For more than sixty years the location of the u-boat's wreck eluded divers. In 2012, a team found it. This was the last undiscovered U-boat in diveable waters off the Eastern Seaboard of the United States, more than three hundred feet below the surface, nearly one hundred feet deeper than the sub in Shadow Divers. This is the story of their twenty year quest to find the "Holy Grail" of deep sea diving and the tenacious efforts to dive on this treacherous wreck.