Frank answers about swimming naked
People who didn't experience boys swimming naked in the YMCA and in many physical education programs in the public schools in the US find it hard to believe that this was done. Yet this was the practice. Boys swam naked in the YMCAs and in school physical education classes from the time pools were first installed in these institutions in the late 19th century until the 1970s. Many men over 50 testify that they swam naked in high school and college. Many people under 50 don't believe them. But it was the practice and there are some pictures to prove it.
source: Article 'Frank Answers About Swimming Naked' by Frank Senn; www.frank-answers.com/frank-answers-about-swimming-naked/; Frank Answers; 15 August 2016