Flushing a running vacuum with water
But this resulted in dust being deposited on the impeller of the vacuum, and that threw it out of balance, causing extra noise and vibration.
I had taken a ShopVac like this apart before, so I knew that, unlike regular vacuum cleaners, it has a separate fan and air stream to cool the motor. So I figured, it should be possible to flush the running blower with water without getting the motor wet or getting zapped.
So I put the blower unit upside-down in the grass, with a piece of wood to prop up the float ball (which normally blocks the air flow vacuum if it gets too full of water). The switch on the ShopVac is in the on position so that I can start it by plugging it in.
Those that do stuff tend to be more interested in just getting stuff done, and assess risk on a case by case basis, rather than by repeating some safety mantra.
So maybe this technique could be useful to you. But if you think it's dangerous, then don't do it. Simple as that. Your concern should be your own safety, not mine.