My lastest insanity in the water weaponry departement.

2.x Gallon water tank, ball valve for quick firing, quick release thing to plug the hose in, with a valve to stop the water from coming back out. 3 different pipes to attach at the end to change the precision or volume of water launched. The tank contains a membrane filled with air and can go up to 200psi.

It takes between 8 and 12 seconds to reload, and can fire with the hose still attached.
And i have a 40Mb video of it,
here. Stupid camera doing huge files when it could be smaller. But it's worth seeing.