Water and electricity don't mix well.
We were 'endurance' testing a high-pressure pumpset with lots of control and monitoring gear attached, designed to give warning if 'anything went wrong'. Container-sized generator. Coolers to keep the water temperature down. Big set up, and because it had to run for a few days, access was restricted for safety and security.
I realised something was amiss when walking past the building, I noticed water coming out of the ventilation louvres 25 metres above ground level, then a shoe float out of the emergency exit. It's not easy stopping these 'temporary' lash-ups especially when there's an upside-down tropical-rainstorm going on in a building packed with electrical equipment. Incredibly, all the electrical and electronic gear survived. On subsequent tests, I made sure we had a stop button outside what was laughingly called the 'Control Area'.