This happened when I was 20, twenty years ago !
It was summer, and I had a cruise sailing training on a sailship across the French Mediterranean sea, for seven days. We were six in the crew, the instructor, four young men (including me)... and a young girl, 18 or so. The ship was pretty big, 33' or so, so we slept inside when at sea or in ports.
Since the weather was fine, we used to be in bathsuits all day long.
When the wind was low, we used to take sunbathes, and the girl removed her top and let us see her incredible breasts. Not so big, but her nipples were, and were shaped as half spheres the size of a half tennis ball, and mounted on top a smooth, bigger cup. Of course all five men were horny seeing her, and were willing to touch those beautiful nipples, but she did not let us touch them! Apart from that, she was dark haired, and was a very nice girl. Unfortunately, I don't remember her name...
One day the ship moored in a crick not far from Marseille, and everybody jumped into the hot sea water to swim. Everybody, but the girl and me! 'this is my chance', I thought, and very slowly I approached here, looking her into the eyes, until I was close enough to kiss her. And I did! And she liked it! God, the first time I touched her nipples, I was shivering.
The day after, we sailed again, and I was designed to be the captain for one day. To my surprise, one of the boys asked me if he could touch my girlfriend' nipples! 'ok but you will do the cooking for the day', I replied, without asking the girl if it was OK for her! But she played the game, and let the boy touch her breast... but not kiss her, that was for me only, she said.
Soon after, the other boys asked for the same favor, one after each other, and I accepted, giving them various chores to do in return, and they seemed to be happy with that! That was very funny.
In the afternoon, all crew were in the rear cockpit of the boat, except me (I was computing the route with the map inside the cabin), and the girl , who was standing on the cabin stair and talking with the others, only her top being visible to them.
While she was talking, I approached her from behind and under, being invisible from the others, and I let my hand climb along her leg and under her skirt. To my surprise, she had nothing under her skirt ! So I began slowly rubbing her pussy, then fingering her, still while she was talking ! I knew she tried not to show anything to the others, but I knew she was enjoying what I was doing because she was so wet ! I'm sure she had an orgasm, because suddenly l felt more juice onto my hand and she shivers a little, so little... But her voice kept so calm I couldn't belive she controlled herself so much. Did she orgasm, or not ?
Just after this we both climbed up to the cockpit as if nothing had happened. But in evening I asked her, whispering, if she had been pleasured by what I did, and she just took my forehand and pressed it strongly. God! I instantly became rock hard.
It' so good to make a girl come when she doesn't want to show it to other people!