Using a toilet has never been more complicated than it was when aboard a Second World War era German U-boat. The high-pressure U-boat toilet, which allowed the crew to use the lavatory at greater depths than before, was a fiendishly complex device that channeled waste through a series of chambers to an airlock where it was expelled into the sea. Using this toilet was so complicated that it required special training, which only a few crewmen on each U-boat would receive. This training involved having to remember the exact sequence of valves to open and close so as to expel the waste into the sea while ensuring that the sea didn't rush into the submarine.
And so it was that on 14 April 1945, aboard U-1206, a Type VIIC U-boat cruising 200 feet below the surface of the North Sea, ten miles off of Peterhead (a town on the coast of Scotland), Captain Karl-Adolph Schlitt decided to answer the call of nature. U-1206 had only just begun her active service as part of the 11th U-boat Flotilla two months before, after a long period of training. Indeed the U-boat's career since her commissioning on 16 March 1944 had been very uneventful, having never sunk or damaged an enemy vessel and having never lost a member of her crew. However, all of this was about to change when Captain Schlitt went to the toilet, during his first real patrol in enemy waters.
Exactly what happened when he had finished his business and was flushing the toilet is a matter of historical debate; there are two principle schools of thought concerning the matter. The first theory is that U-1206's high-pressure toilet simply malfunctioned, at least this is what Schlitt himself told a German researcher after the war had ended. The second theory, admittedly far more widely reported and believed, is that the bashful submarine captain decided not to call the specially trained crew member and instead had a go at operating the high-pressure toilet himself, at which point he got the precise sequence of valves wrong. In any case the final result was the same: the unfortunate Schlitt was blasted by sewage and sea water as the North Sea began flooding into the U-boat's lavatory compartment via the toilet bowl.
All hell broke loose inside U-1206. By the time the toilet specialist arrived on the scene and the toilet valves had been shut, sea water had begun draining into the forward battery room, which was directly below the flooded lavatory compartment. A chemical reaction between the water and the battery acid ensued, producing large quantities of extremely toxic chlorine gas. This forced Captain Schlitt to order the U-boat to surface so that the interior could be vented. Since the submarine was at that time cruising only ten miles off of the Scottish coast, it was spotted almost immediately by a British aircraft and bombed. Unable to submerge and escape due to bomb damage, Schlitt scuttled the U-boat, making U-1206 the only submarine ever to be sunk by its own toilet.
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