 Early on the morning of 15 May "U-43" opened fire with her deck gun and anti-aircraft guns on the 488 ton French three-masted sailing ship "Notre Dame du Châtelet", en route from St. Malo to the Grand Banks of Newfoundland to fish.After being hit by 45 shells the ship sank.Lüth suspected that the vessel was reporting the positions of U-boats to Allied forces, while the 10 survivors thought they had been attacked by a British submarine.