I learnt to masturbate when I was 14, which seems quite late compared to many here!
I was on the local beach (I live in a holiday resort) in the summer, and there were a lot of attractive young women in skimpy bikinis. I'm not lesbian but they were making me feel all funny inside.
I strolled away from my family to some rock pools, and saw what looked like a 16-year-old girl and a slightly older guy having sex, naked on the far end of the pool in 'doggy style' (I didn't know this at the time) facing away from me. They made all sorts of moans and grunts, and the actual act made a weird slurping.
I slid under the water a bit behind a rock so I couldn't be seen, and began to rub this weird sort-of-itch between my thighs. I slid a hand under my swimsuit and it felt extra slippery. It also felt VERY nice!
I used my thumb and fingers to gently massage a harder part between my flaps, and I was quivering it felt that good. Pretty soon, I was shaking all over and it felt awesome. I had to shut my eyes as I began to splash about.
I opened them a little later when the feeling went, and saw the guy and the girl across the beach, this time clothed. They chuckled, and waved. I figured they must have heard me, and blushed!
I now masturbate 2 or 3 times a week in the day, and every night in bed.