Mixed experience this weekend...I was visiting friends in NC for a few days and decided to get a day pass at their gym...a co-ed YWCA. I was pleased to discover it had open showers. Open lap period ended, so the other male swimmer and I returned to the locker room and hit the showers. He was friendly and struck up a conversation with me, complaining about the schedule, etc. After I washed my upper body, I slipped off my speedo to rinse out my suit and proceed with downstairs cleaning. He seemed completely unfazed by my nudity, neither staring nor averting his eyes, just maintaining the conversation naturally. He never stripped his off, however, and turned away to briefly lower them and wash his junk. After showering, he faced the wall to drop his suit and wrap with the towel and use the ringer on his suit. As it turned out, we shared a locker cove so we continued our conversation. I had dropped my towel in a bin, so I was naked, but he was still wrapped in his. He started to put on his underwear with the towel still wrapped, so I expected a full towel dance, but he finally pulled it off so he could pull his underwear up.
It was interesting that he was completely comfortable seeing another dude's junk (my penis was in his field of view for 10 minutes or so in the shower and again in the locker area) but was quite modest about his own nudity (but not so modest as to not drop the towel at the end). He was probably a bit larger than average and definitely quite a bit larger than me, so size insecurity couldn't have been a factor.