This happened a while ago when I lived in San Diego... I enjoy finding new places to masturbate. I was in my car parked in a parking lot near the beach, and was enjoying the view of the women in their bikinis. The longer I sat there in my car, the harder I got.
I pulled out my dick and started stroking it. I was careful to watch for anyone walking around (or so I thought), and was in a pretty safe spot near the end of the parking lot. So there I was, pounding away with both hands, enjoying the view, and I became oblivious to what was around me.
Turns out that two young women (maybe early twenties) had walked up from behind my vehicle without me noticing. Just when I was about to cum, I looked over to my right and saw them staring at me. I realized I was past the point of no return, and decided to keep going. As cum started to spurt out of my dick, they let out a 'woohoo!' and clapped, they seemed to enjoy the show! I finished stroking it, and left a mess after maybe eight to ten spurts of cum. It was all over my hands, pants, shirt, steering wheel, etc. They left without saying anything else; I cleaned up as best I could, and left.