A key principle in user interface design is that the normal operation of a system should be easy, and that abnormal operation should be possible only if you do it on purpose. This is especially important if the operation is common, needs to be done under time pressure or high stress, or if the consequence of error is catastrophic.

Pooping frequently satisfies two of these three criteria, and as this story demonstrates, it sometimes also satisfies the third.

Therefore an important lesson: If flushing the toilet can only be done safely by a single highly trained individual aboard your submarine, and if anyone other than this person – including, in this case, the combined efforts of the Captain and an engineer – cannot do this without causing the entire ship to sink, then you are doing your design spectacularly wrong.