The water ones are the worst, it seems that lube residue and or semen can cause a hydrolysis reaction causing the hydrogen and oxygen to seperate, if close to an ignition source when you take off the cock pump
the hydrogen ignites, shoots the pump through your window onto the front lawn and the backdraft ignites the short and curlies a bit like a North Korean missile test!
There has been some cases in asia, of the penis being completely obliterated and unable to be reconstructed!
just trap it in the door and give it a good stretch every week!