Three different German U-Boat wrecks from WW1 and WW2 tell the story of the threat posed by the unseen weapons of war. Maritime archaeologist, Innes McCartney, finds the UC66, the first German U-Boat to be sunk by a plane. The otherwise successful U-87 discovered in the Irish Sea was rammed by an Allied ship. And the identity of the rubber coated U480 confirms the German success in developing stealth technology.