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.
Lived in Southern NJ, very few schools had pools. If I recall AC High School and Holy Spirit HS. had swim teams.