Frank K. Kelly "Last Ship Home."

The Lintons, a honeymooning couple, embark for America from Great Britain aboard an overcrowded neutral ocean liner at the outbreak of World War 2. Also aboard the liner is a woman out of the man's past (she's possibly still his mistress). A day or so out of Galway (the liner's last port of call before heading west across the Atlantic), the liner loses much of the extra illumination that had been lighting up its American-flag painted sides (author Kelly notes that "a neutral ship must be illuminated by night and day, and plainly marked") - naturally at this precise moment a German U-boat appears and challenges the vessel. Women and children are hastily placed in lifeboats as the ship's officers, crew and male passengers wait for the worst. At the last moment the failed lighting system miraculously starts up again and the U-boat is forced to acknowledge the fact that the liner is indeed neutral. Women and children return to the ship and all resume their uneasy voyage to the safety of America.