Happened 3 times that I can remember at a local gym shower. Once when alone and started to fantasize, which is odd because I don't usually fantasize much. Once when I was showering next to another and either got excited or nervous, I honestly don't know why. He noticed and wanna gonna say something, but I got embarrassed and left. Last time was with one guy who had a huge semi-hard dick and clearly loved showing it off. His hour long showers were my first hint. Usually there were a lot of people in there when we'd shower, but one time it was just him and me. Took awhile for one of us to make the first move, but it was pretty obvious with the way he was playing with that he wanted attention, which I eventually gave him. Never saw him again though. Don't know if he was eventually threw-out, or just stopped going there. There was one guy who's dick used to stick straight-out, but I wasn't convinced it was because he was hard. Just seemed to be how it naturally was. I think a lot of guys are semi-hard at times, but those are the only ones I can remember.