I once went to my local swimming pool for a dip in the pool, after a while it was time to get out and go, I needed a pee too so went to the toilets that you had to walk past the open showers to get to.
I entered the showers and in the showers was a couple of boys about 11 or 12 years old under the corner showers and just outside the showers but still inside the mens shower area was a couple of girls about the same age giggling at the boys who I think had just flashed their cocks at them. The urinals were in full view of the girls who even though I had entered the area stayed not bothered that I was there, I went to the urinals to have a pee before showering and pulled the front of my trunks down exposing my cock and had a long pee which the girls could clearly see me having.
I finished peeing and went to the showers and as usual I took my trunks off to shower naked and went and stood under the shower at the end and close to the girls who still did not leave, they just stayed and watched me showering. Well this got me turned on so I decided that if they are going to watch me I would give them a bit of a show, I stood under the shower and rinsed off and started to rub my cock which soon got hard, the girls obviously see this and at first looked surprised but then giggled a lot at seeing my erect cock, I asked them if it was the first time they had seen an erect cock and they both said yes.
It was not long before I felt the familiar feeling of me coming to an orgasm and sure enough I then shot my load in front of the girls and the boys. Wow what was that the girls asked, so I told them that it was what happened when a guy wamks and has sex with a girl.