Going into the military in the early 1970's we had open showers and latrines. There simply was no privacy and no one cared. That's the way it was, nothing sinister about it.
BTW I think girls wore swimsuits because of the variety of feminine hygiene options used at the time. Some were primitive by today's standards.
I was in the Marines.................
My high school didn’t have a pool, but girls could get out of gym class during their periods. I had an aunt who hated gym class so much, she pretended to be on her period every week and never got caught. I’m guessing girls probably got out of swim class during “that time of the month.”
I think in England it may be normal to swim in the nude. I was at a hotel pool (in the US) recently, and some young kids were swimming in the nude. A hotel employee went up to their mother and told her that kids were required to wear bathing suits in the pool.
I was around in the 60s and no one I knew swam nude in public pools. I had swimming lessons in the mid-60s, used pubic pools and lakes and seaside. If it was 2-3 guys at a remote lake, we’d swim without clothes. Always used a swimsuit - as did everyone else - in all other locations and certainly in pubic pools.