I do triathlons occasionally and must therefore do some swimming after work in preparation. It took some getting use to but gang showers are now no problem. I do remember though, the first few times I used them, I found myself getting hard at the idea of being completely exposed in a public setting. I would sort of pick a corner spot in the shower and stay turned around with my butt facing outward until I softened up. I have a thick penis of average length and it was interesting seeing the incredible variety of sizes, shapes, tints, head size etc. of this part of the male anatomy.
One thing that was, and still is, a turn off are guys with horse dicks that so obviously parade around the locker room to make sure everyone has seen them. It seems there's always one in every public locker room facility. Personally, I'd hate to have to stuff a 10-12 inch dick in a speedo...........would be totally embarassing.