Luv it all!
When I was 14/15 I would go swimming with my best bud's dad at our open all year swimming pool. After our exercise we would return to our seperate dressing room.
They had a few small holes in the partitions of the booths and I could see him drying off, then jack off, in the towel we would get from the pool clerk. He had a cock like Godzilla and he would spurt a flood of cum on the pool's towel
I would jack off my near 6 incher when he did although it was hard to hold back 'cause he was so sexual masturbating. Anyway, I matched him stroke for stroke and did so for about 3 years.
I never told my best bud I jacked off when his old man did 2 to 3 times a week. Why ruin a good thing, when he and I were jack off buds already.