My first girlfriend had a sauna in her basement. While it wasn't a public sauna, we got sweaty more than a few times.
One time that did not result in sex will never leave my memory, though. We were staying in Austria with friends and I went down to work out. After the workout I went and sat in the sauna. There was another guy in there sitting on his towel exposed. Not thinking much I did the same thing. As I sat there a few other people came in and out, some of them women. I realized finally it was a coed sauna and decided to stay minute.
After a few more minutes. In walked one of my wife's friends, who had also just finished working out. I thought about covering, but people were really doing that. Plus I was hanging really well, so I thought I would roll with it. She said Hi, turned around, picked a spot kind of across from me and then dropped her towel. She had an awesome milf body. I had always wanted to see her naked and now I fianlly had.
We sat there and made small talk. I couldn't help glancing more than a few times I I caught here couple times doing the same. I was amazed I didn't get an erection, but it go to be a pretty plumped up softy. (Not as big as my pick, but swollen.) I have to say I wanted to fuck that woman so bad I was lucky there was another person in the room.
I always remembered that when I saw her after that. I wonder if she thinks about it too.