The U-1206, a German Type VIIC submarine "the workhorse of the German U-boat force" was one of the late model boats fitted with a new high-pressure toilet allowing the toilet to be used at greater depths than before (though in reality the culprit was not actually the toilet itself). Flushing these facilities was extremely complicated and special technicians were trained to operate them.

German U-1206 [Via The Scotsman]

A cross-section of a Type VIIC U-boat [Via Wikipedia]

On 14 April 1945, 24 days before the end of World War II, while U-1206 was quietly cruising at a depth of 200 feet (61 m), 8 nautical miles (15 km; 9.2 mi) off Peterhead, Scotland, 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.

E-machine room, behind the diesel engine room [Via Wikipedia]

Once surfaced, at the same time the crew managed to clear the gas by blowing clean air into the U-1206, she was discovered and bombed by British aerial patrols causing extensive damage which left U-1206 unable to dive. The hopeless situation forced Schlitt to scuttle the submarine. The Commander's U-boat had no choice but to destroy the secret material and order Abandon Ship to save his crew. 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 located.

It recorded Captain Karl Schlitt as stating: “I was in the engine room, when, at the front of the boat, there was a water leak. What I have learned is a mechanic had tried to repair the forward WC’s outboard vent. The engineer who was in the control room at the time managed to make the boat buoyant and surfaced, despite severe flooding. Meanwhile the batteries were covered with sea water. Chlorine gas started to fill the boat. We were then incapable of diving or moving. At this point, British planes and patrols discovered us. I let the boat sink.”

A Stork - U-1206 [Via uboat.net]

During survey work for the BP Forties Field oil pipeline to Cruden Bay in the mid 1970s, the wreck of the German U-boat scuttled by its crew off the Scottish coast were found at 57°21′N 01°39′W in approximately 70 m (230 ft) of water by a team of divers from the Buchan Divers group found after a 12 year search. Divers explored a spot 12 miles off Cruden Bay, Aberdeenshire, and, at a depth of 86 metres, became the first people in 67 years to see the wreck.

Jim Burke, who led the expedition, said: “The feeling on seeing it was one of elation and excitement. We found ourselves looking at a unique piece of Second World War history. The buzz was amazing. This was a significant bit of history. We have spent so much time and energy looking for her. It was great that we could finally see this boat that we had spent so much time researching”. The IT engineer added: “Most dives we do involve discovering a wreck and then finding out her story. This was the first one where we have known all of her story beforehand, but finding her remained elusive until now”, The Scotsman reported after discovery.

The site survey performed byRCAHMS suggests that the leak that forced U-1206 to surface may have occurred after running into a pre-existing wreck located at the same site. 

German U-1206 [Via X-Ray Mag]

An uncorroborated theory from a relative of a crewman that the toilet fault was a cover story for the captain who had wished to surrender has been dismissed by nautical archaeologist Innes McCartney, who is completing a doctorate in U-boat wrecks at Bournemouth University, The Scotsman reported.