(english is my second language I might make some bad spelling)
It happened when I was 15. I was in a Scout group with both boys and girls. We went in a camp for a few days to have fun and learn survival skills.
The first day, we swam in the nearby lake and when it was time to put on our normal clothes we had to go to a little shack with cabins only separated with curtains. I was kinda late and everyone already had a cabin.
I chose the closest to me and opened the curtain. There were three fully naked girls (they were all very beautiful) just chatting while changing their clothes. It took them a few seconds to realise I was there so I enjoyed the view. They screamed and laughed at the same time. I quickly escaped and went in an empty cabin.
While I changed my clothes, I heard someone giggle near my curtain. Suddenly, the three girls from before open the curtain and look at me. I had a boner and they all laughed at me. Thank god most people already left the shack so no one else saw me. I closed the curtain and put on my clothes. I decided I wouldn’t tell the adults because I had also seen them naked. I saw two of the girls watching me on the way to the camp.