I've been on nude beaches before where there were probably 10 to 20 naked people in my visual range, there were probably more than that but they were further up and down the beaches. This was in Greece and in Croatia.
After swim meets in college, there could be up to 30 naked dudes in the open shower room and surrounding locker room area. Because mutliple teams would be at meets in some cases, there could be a lot of guys in smallish locker rooms. Often there were not that many shower heads in the room, so some naked guys would be waiting outside the shower area for a shower to open up. Sometimes guys would strip out of their speedos before getting under a shower, others would keep them on until they got to their shower.
I fuckin loved after a meet when our team would win. We'd be so proud and full of ourselves and the testosterone would be flowing strong. Most of the time we'd be sharing the locker room with the other teams. My relay group and I would strip out of our speedos as fast as we could and walk around buck naked showing off. Thinking back, I think I was totally trying to position a superior CMNM kind of situation around the other teams. Some of the other teams' guys would join in, others would keep their speedos on maybe out of shame for losing. At least that's what I liked to think to myself to feel even more proud of our accomplishments.
One time we were showering and a couple guys from a losing team walked into the shower room with their speedos still on, my buddy Ben shouted "hey bros, just because you lost doesn't mean you have to hide what you got!" some of the guys walked out of the room!