My wife and I were on a Mediterranean cruise and I had just returned the life vests to our balcony cabin after our drill, when I realized that the ship was starting to move out, and my cabin was directly across from another ship in port. On an impulse, I quickly stripped down, turned all the cabin lights on, and opened the door to the balcony. I stood up on a chair so that my dick could be seen above the railing on the balcony, and proceeded to stroke myself and show off my assets to passengers on the other ship. It was exciting because they were so close and I saw some that were clearly looking right at me.
As we started to move away, I went out on the balcony and stood on a chair there to give a better view. By this time I was so excited that I went for it and ejaculated all over the balcony. It was quite an unplanned adventure, but it was wildly exciting to anonymously expose myself to strangers, and jack off publicly in a context where I had no chance of getting caught.