Comment below if you swam naked in school or indoor community pools. The girls were lent sterile swim suits - for the exact same reason.
Swimming pools were introduced in the U.S. by the YMCA in the 1880s. In the following 25 years, those pools became major sources of sustainable revenue. Boys drowning was the second leading cause of death, before age 16, after disease. The Y offered both organized lessons and teaching the fastest stroke possible, verified by the Olympics, the crawl stroke. In that pre-TV era, being the fastest was a big part of social entertainment.
However, in 1906 Edwin Foster, a Northwestern medical school graduate working at a YMCA, (a typical situation), tested the water and discovered it was contaminated. This was a major threat to the business income because cholera and typhoid were transmitted through water. These diseases were still causing widespread, fatal epidemics that closed down cities.
In 1906, the standard YMCA pool procedure was to drain the pool and refill it once a week. (This actually continued into the 1920s. In one case, in Spartanburg, SC, the 45,000 gallon pool was emptied and refilled twice a week into the 1920s.) In most cases, the men and boys swam naked just as they had in rivers and farm ponds.
The YMCA National Council recommended the use of sand filters, which were known to be effective. What's available in the literature shows that by 1910 the first pool recirculating pump was installed and by 1913, chlorine chemicals were being added to the water. (The Federal government was just beginning to require chlorination of public water.)
In 1926, the American Public Health Association published the first guidelines for swimming pool management. These guidelines were updated every one to three years, as needed. Those guidelines recommended that males swimming separate, take a soap shower and swim nude. Unadorned, undyed tank suits were recommended for females.
The APHA pool management guidelines were not written about nude swimming but about keeping pools sanitary and that meant keeping the water disinfected. Consequently, male nude swimming was recommended in every edition until 1962. When one studies the APHA guidelines and those issued by other states, such as by the State of Illinois in 1948, (where they flatly state that sanitation is best preserved if people are separated by gender and swim nude. That came from fourteen of the best swim coaches, sports physicians, sports professors and water sanitation specialists the State could put on a board.)
Chlorine was difficult to use effectively because pH had to be managed in addition to having enough chlorine to kill bacteria. It was not until 1939, what was called the break point in water chlorination was discovered. It was then possible to make chemical tests that pool managers could use. However, WW II intervened and the equipment to do automatic chlorination was not available until the late 1940s.
A few months after the U.S. entered WW II, the L-85 Regulation was implemented. This mandated the minimum use of cloth for clothing since it was needed for munitions. It also stopped the sale of home sewing machines. During that time, it became patriotic for men and boys to swim nude. A review of camp archives shows that nude swimming at camp became virtually universal during WW II. However, the hygiene and convenience was recognized and nude swimming at camps continued into the 1960s, beginning to fade in the mid-1950s.
In 1948 and 1956, the Boys Club Operations manual required and then recommended, respectively, boys swim nude. The YMCA and Boys Club Operations manual both stated it was incumbent upon the boards of directors to abide by the state and American Public Health Association guidelines.
The public school boards responsible for schools with pools also had to abide by the state public health and APHA pool management guidelines. That's why we swam nude in school pools.
By the way, pool filters get clogged with fabric fibers even today. (Case-in-point: put a load of shirts in a clothes dryer after cleaning the lint filter. After they are dry, check how much lint is in the lint filter.) It wasn't until the late 60s or early 70s that nylon suits became widely available. However, the fibers clogging the pool filter was only part of the story. What the Public Health officials wanted to avoid was telling all swimmers that their swim suits were probably contaminated from polluted water from their last swim at the beach or outdoor bathing place. As corroboration, recall that they used to have laundry tubs of chemicals you were to drag your suit though and then rinse, when you swam at a co-ed city pool.
The 1948 State of Illinois Public Health Association pool management guidelines states specifically that to preserve female modesty, they could wear unadorned, undyed tank suits, after they took a nude soap shower. That's why females wore suits.
Now as for YMCAs and nude swimming. If one researches this Nation's newspapers, one will find that when YMCAs ran ads for learn-to-swim, it was stated in both the display ad and in the reporter's commentary that boys swam nude and only needed to bring a towel. In a few cases, the boys were photographed swimming nude and the photographs published in the town newspaper. It was a socially expected practice since they were men and boys and had nothing to be ashamed of.
By 1962, most Americans lived in suburbs and most boys, (who did most of the swimming), did not swim in polluted outdoor water but swam in city pools. Automatic chlorination was controllable to adjust for the contamination in pools. Medicine had conquered Polio and the medical profession was confident curative medicines could stop outbreaks of any disease that might be transmitted by pool water. Also, in 1962, there was no public outcry to end male nude swimming and there was no feminist pressure.
In 1962, the American Public Health Association dropped the nude swimming recommendation because it was no longer needed to preserve public health. This insight is important because it underscores why male nude swimming was recommended and required for more than 50 years. The Y and schools continued nude swimming into the 70s, and in a few schools, into the 80s.
So many people today do not know about the era of nude swimming. After mentioning swimming naked in High School to people in “you won’t believe me… but” conversations, people thought it was creepy or that the instructors were pedophiles. Records shows a few were but the vast majority of the thousands who worked with boys as swimming teachers, coaches, or life guards were good decent men. Naked swimming was just the way it was, it was seldom sprung on the class as a surprise. Typically the students knew from a year or two before that when they reached that point they would swim naked.
It wasn't urban legend; just a normal part of life in a different and much more self-confident time.