On March 28, 1945 the submarine departed from Kiel for its first training patrol in the North Sea, returning on March 30. The submarine departed from Horten for a one-day patrol on April 2, and its first active patrol began on April 6, when it departed from Kristiansand. On April 14, while on patrol, the vessel sank after the toilet was operated improperly.
On April 14, 1945, 8 miles (13 km) off Peterhead, Scotland, while cruising at a depth of 200 feet (61 m), misuse of the new toilet caused large amounts of water to flood the boat. According to the Commander’s official report, while in the engine room helping to repair one of the diesel engines, he was informed that a malfunction involving the toilet caused a leak in the forward section. The leak flooded the submarine’s batteries (located beneath the toilet) 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. Schlitt recorded the location as 57°24′N 01°37′W but the wreck could not be relocated.
During survey work for the BP Forties Field oil pipeline to Cruden Bay in the mid 1970s, the remains of U-1206 were found at 57°21′N 01°39′W in approximately 70 m (230 ft) of water. The site survey performed by RCAHMS suggests that the leak that forced U-1206 to surface may have occurred after running into a wreck located at the same site.
A large number of sources attribute this incident to U-120.
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