In World War II, a Nazi submarine U-1206 was accidentally sunk by?

On 14 April 1945, while U-1206 was cruising at a depth of 200 feet, misuse of the new toilet caused large amounts of water to flood the boat. The leak flooded the submarine's batteries causing them to release chlorine gas, leaving him with no alternative but to surface. Once surfaced, U-1206 was discovered and bombed by British patrols, forcing Schlitt to scuttle the submarine. One man died in the attack, three men drowned in the heavy seas after abandoning the vessel and 46 were captured.