During World War II, countries across the world were making strides and improvements when it came to military equipment. And nothing was more advanced than submarines. The German Type VIIC submarine, for example, was considered to be one of the most advanced hunters of the seas during its era.
And innovation did not only come in the form of actual warfare and weaponry, one of the reasons this class of submarines was considered to be so advanced was because it had new hi-tech gear. For example, the VIIC submarine was able to flush its toilet while staying submerged. This was something that had never been possible before, and the hi-tech toilet required special training to ensure you flushed it correctly.
One of the submarines, the U-1206, actually sank on its maiden voyage due to the captain improperly using the high tech toilet mechanism. Yes, this really happened, a toilet sank a high-grade military submarine. It is, unfortunately, a tragic accident of a real naval engineering dilemma.
You see for years German engineers had been preparing the next generation of undersea plumbing. At the time Allied submarines were using septic tanks, but German engineers thought that the best way to save some precious weight and free up space would be by getting rid of this. The idea was to discharge waste directly into the sea.
This came with unique challenges, how can a toilet flush where water pressure is so high? The system did only work when the submarine was close to the surface, which made the submarine a sitting duck in the shallow waters. German toilet technology improved even more and they invented a deepwater flushing mechanism. But the toilet was so advanced it was extremely complicated to use and would require special training.
Flushing used an air valve to blast out the waste into the sea, so it needed to be opened in the correct order or you would find water flowing into the submarine. Captain Schlitt was not trained as a toilet specialist, and after turning the wrong valve, seawater rushed into the submarine. Ultimately they were not able to save the submarine and had to breach the surface, where they were immediately attacked by British air forces, eventually causing the submarine to sink completely.