On April 16, 1944, the tanker SS Pan Pennsylvania was torpedoed 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 60 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, more than three hundred feet below the surface. This is the story of their 20 year quest to find the 'Holy Grail' of deep sea diving and the tenacious efforts to dive on this treacherous wreck.
