The short answer is that girls were usually never allowed in swimming areas when boys were swimming nude. However, if one goes back in history to the 1800s and 1900s (Victorian and Edwardian eras), it was indeed very common for boys up until puberty (and sometimes even beyond) to swim and "sea-bathe" with girls their age, all the while stark naked (although girls were always clothed).
A huge archive inclusive of actual history book passages, news articles, old photographs and vintage film archives that evidence can be found here:
Yes, here in Germany they do. Our high-school has the outdoor pool open for nude swimming on Sundays from now till September (I have pool duty twice a month). Mostly it's boys - typically 20-30, but some girls, maybe 5-10. The girls who come tend to be from the older years (17 and 18 year-olds), while the boys come from all years (13-18).
So on Sundays were all the swimmers naked at the pool both boys and girls and were there only students swimming no adults. You said there were like 20-30 naked boys and only a handful of girls, why so few girls?
Did the boys just run around swimming and laying down and not care about the nudity and what part of Germany was this?
No girls showed up but we had a female coach who swam nude with the boys class.
When I was I High School (mid '70's) boys swam naked and girls wore longish T-shirts. Separate cases of course but my girlfriend at the time swore that she and another girl once wandered into the life guard office (a windowed booth that overlooked the pool) and saw a class of boys. They didn't stay long because they were worried about getting caught.
That would be the ONLY case of this that I can imagine. The Female swimming teacher would occasionally enter the coaches office during a boys swim class, and perhaps, not knowing the boys were still in the pool have a girl or girls in tow, but it was NEVER expected or at all common. Least where i grew up.
Yes, I think in the USA where nude swimming happened it would be an occassional teacher or an accident where the girls might get a glimpse very rarely, not an everyday occurence.
Never happened at any school I went to.
Maybe some boys-only boarding school or something? I have heard stories such as you alluded do but have never had anyone who had any actual knowledge of any such thing at any school, public or private. I think it is some kind of urban legend passed down from generation to generation... perhaps because of long ago practice at YMCAs.
That includes college (even though most of the dorms were coed and even though the college campsite was defacto clothing optional) there was no nude swimming in the college gym swimming pools.
I have heard about how back in the 40s and 50s when the YMCA was males only, swimming was always done in the nude. I have been told that was true by people who swam there in those days, including my father. Then they started letting women in and that ended that. (Can you imagine how cool it would be if the Y did coed nude swim?) I have never heard, however, of any YWCA when they were women only having nude swimming. This was before my time, but I do not believe the YWCA in my town even had a swimming pool. (Come to think of it, did the those two organizations merge or what?)
Just wanted to add that when I said my college had a lake -- not on campus, was in a rural section of a neighboring county -- intended for camping and such, students in the sixties had decided it should be coed and the university administration never wanted the embarrassment of a confrontation over nudity back in the days of antiwar protests and such -- and by the time that kind of thing calmed down, "clothing optional" had become a tradition. And it was so wonderful -- university eventually got rid of it and it is private land today. Enter "Empire Lake, Spencer, NY" into Google Maps.