I've done this with the water jet in the swimming pool holding onto the lip of the pool with that jet hitting the exact same spot underneath my erection in the area just under the tip. The main difference is I shot out a load of sperm all gooey and going everywhere. It was a motel pool at night, and I was lucky I wasn't caught. There was no hiding my manly mess. At least my swimming trunks were only part way down.