So if I pour water onto a huge dome of metal, it might build up enough of a negative static charge to jump a spark gap? New science exhibit idea!

Water-driven electrostatic generators are really easy to build. The key is to have droplets separate at a point where there's an electric field, which causes the detaching droplet to carry a charge. Properly arranged this can cause an exponential increase in charge with time.

https://en.wikipedia.org/wiki/Kelvin_water_dropper