So this happened on my (18m) most recent cruise on the Carnival Mardi Gras. We were docked in San Juan Puerto Rico. It was later in the day and after walking around old San Juan w/ my family, we returned to the ship and they all decided to go to the pool for food and a movie. I was a bit tired and so I would stay in the balcony cabin. They left and I took a shower to wash off my sweat. I finish my shower and I step out onto my balcony nude to feel the nice wind on my body. When across the way there sat the beautiful Valiant Lady from virgin cruise lines. They are pretty close to us and you can see into some of the rooms without binoculars, and I see a woman in her late 30s early 40s in the same attire I am in.(Absolutely nothing) If you haven't been on the Mardi Gras balcony, you should know that they are glass and completely see-through. We both see eachother and wave. I thought she smiled slyly but there was a distance between us, she got on her hammock and spread her legs wide so I could see her pussy. I saw her hand slide over and into her. I started to get hard and I started to stroke my dick. She continued to finger herself. After a little while I lose control and cum all over the glass guardrail. I quickly go back into my cabin to get tissues to clean it up. I clean it up and look back over to the Valiant Lady, and I see the woman leaning on her balcony guardrail with her tits resting/hanging over it. She waves and blows me a kiss and goes back inside her cabin and closes the blinds. I finish cleaning up and go back inside to get dressed.