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アメリカ

昔のアメリカの学校の水泳では男子は全裸で泳ぐ規則だった
https://qph.fs.quoracdn.net/main-qimg-52809a39569deebbabf64654bfe5c7dc
http://myhotzpic.com/ymca/ymca-nude-swimming-school.htm

Is it true that boys had to swim naked in swim class or the YMCA in 1960s or 1970s?
https://www.quora.com/Is-it-true-that-boys-had-to-swim-naked-in-swim-class-or-the-YMCA-in-1960s-or-1970s

Yes, it is true.