Cum floating around in a public pool?! Is that hygienic??
My ex used to prank me sometimes.
We were at a nudist resort once, in the middle of a crowded day, naked playing around in the pool. She didn't know how to swim and she wanted me to try help her learn. So I was holding her in my arms while she flapped around.
At one point she lost her balance and jumped on top of me to hold on; but she jumped a little too high and I ended up with a face full of her big tits while holding her by her butt. As she slid down my body with her boobs pressed against me I got an instant hard-on.
When she realized I was hard she chuckled and threw her legs around me. I was trapped. She was now sitting on my hard cock. We were chest high in the water so people couldn't have seen what was going on. She wiggled and bounced around a bit which made my erection even more throbbing. I whispered in her ear: "What are you doing?!" and she just grinned!
She then moved away from me, tugged my dick a few times; and then she just decided to leave the pool! She just walked away grinning! So there I was in a nudist pool in broad daylight, with people all over the place, and a raging erection. I tried to wait a few minutes but my cock was not getting soft. Finally I decided to risk it, jumped out of the pool and made a beeline for the showers. It took a little while before my erection finally went away. I'm not sure if anyone saw it.
When I went back to my wife she was naked rubbing sunscreen on her lounge chair. She grinned again, and sarcastically asked: "Well...what's wrong?!" and laughing. Congratulations: she had punked me!