From Newsgroup: alt.folklore.urban

On Monday, December 28, 2020 at 12:43:40 PM UTC-6, Douglas E. Roberts, Author wrote:

On Wednesday, October 27, 1999 at 3:00:00 AM UTC-4, K. D. wrote:

My high school had a swimming pool, and part of PE involved weekly swim class. As for most PE classes, swim was not co-ed. We girls brought our own towels and other necessities, but were given suits every swim period, which we turned in at the end of class to be laundered.
The door from the boys' locker room to the pool was locked when the girls had swim, and vice versa, for obvious reasons. But, especially since it was
common knowledge that the boys wore NOTHING during swim class. Zip. Nada. In the buff.
A former male classmate of mine came through town a few years ago, and spent
the night at our house. The topic of the boys wearing nothing for swim class somehow came up, and my husband could NOT believe it. He said that he
wore a suit in his HS swim class, and was convinced that the story of the boys wearing nothing was a massive joke perpetuated by the boys to tease the
girls. No amount of persuading would convince him.
In my particular graduating class, the knowledge of the boys swimming nude was especially well-known due to an incident, which was so memorable that it
was specially mentioned by the M-C at our 20-year reunion. One of the male members of the swim team was planning on doing some extra swimming during a
free period he had one day. Thru an incredible coincidence, he was unaware that a girls' class was currently in the pool, but more importantly for some
unknown and unlucky reason, the door from the boys' locker room had been left unlocked. You guessed it -- he walked into the girls' swim class stark
naked!
Even telling my husband of this story would not convince him. Two years later, we were in Seattle, and visited another former male classmate of mine, who verified the story of the males swimming nude. My husband remains
convinced (so he says), to this day, that it isn't true.
I can't PROVE they swam nude, but we always accepted it as truth. My brother-in-law, who went to the HS on the other side of town, reports that they wore suits in swim.
Are there any males out there who can attest to this practice? More importantly, WHY was it done?

https://dougrrr.wordpress.com/2020/12/28/swimming-naked-at-the-ymca/

Answer
Nude swimming in public schools in Michigan from the mid 1920's to 1980 was the rule for the boys in the city of Dearborn and it was thought to be a public health issue to have cleaner water when combined with a soap shower before swimming. It ws thought that boys swimming nude was a normal sort of thing and commonly accepted.
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