A mysterious lost WWII submarine, German U-boat U-455 is discovered off the coast of Italy at 120 meters deep. For Lorenzo del Veneziano, an underwater marine archaeologist, it's an amazing sight. The U-boat is intact. It stands almost vertically at the bottom of the sea, its hull stuck in the sediment. What is the story of this ship? The history of U-455 and cause of the sinking are revealed.