jetting it
"jetting" or "jetting it" is commonly done by old creepy men in public swimming pools. Essentially it's when a guy or girl uses a pool or hot tub jet to masturbate thus "jetting it"
guy one: oh shit dude!! that old man is jetting it!!
guy two: fuck! i didn't need to know that
guy two: oh man im shook, im shook
guy two: im never setting foot in this hot tub again!!!