The first time anything exhibitionist happened to me we were on Hove unofficial nude beach in the UK. My gf had started to play with my dick on the beach which wasn't quiet and wasn't busy either. I thought we were being discreet and I just closed my eyes and rested back on my elbows while I enjoyed her getting me hard. She just kept going getting more enthusiastic and after a few minutes I couldn't hold it anymore and shot my load all over her hands.
I opened my eyes and sat up. It was only then that I noticed that my gf was putting on a show for two other couples who were watching. Both of the men were hard and the women were smiling, one of them was playing with their partners dick. This pic attatched is of Carla putting on more of a show there.