Nude pool party

Some years ago, a friend of mine invited me once to a sleepover. We would drink some beer, play video games, watch some movies, etc. It was around 3 a.m. when we decided to go to the rooftop. There was a swimming pool in the rooftop and I had the idea for us to have a swim. His brother went to get some towels while me and my friend were stripping. At the first moment, we were in our underwear only. Them both jumped into the pool on underwears, but I stayed outside. I didn't bring any extra underwear with me, and that one maybe would not dry until I get home. Well, I was a little drunk and there were only us three there, so I took my underwear off and jumped into the pool naked. It was dark on the rooftop and them both didn't see I was naked until I go out the pool and come back. When they saw I wasn't wearing anything, they also took their underwear off. We stayed there swimming for almost an hour, everyone naked. Luckily no one came while we were there. We went back to the apartment, took a shower and came back to video games and beers. My friend and his brother got dressed, one of them shirtless, but I decided to keep naked. I asked if it was okay, they said yes, so I did it. I spent the rest of the sleepover nude.