Here in Minnesota a few years back a toddler sat on the pool drain and it sucked out her intestines. She died nine months later.
The Abigail Taylor Pool Safety Act http://www.poolsafetycouncil.org/article026.html
North Sea back in the seventies. Divers were in a saturation dive and then came back to the surface but under pressure in the chamber. A pressure failure happened while a diver was on the toilet in the chamber. Not good at all.