During peak times, my YMCA wants 5 to a lane. It’s tough because you have competition level swimmers, people who were competitive swimmers and casual swimmers. Some folks are having fun, others are pushing.

Customs vary by when and where you learn them, and it’s feels very hostile, especially for casual swimmers. (In my online experience, the closest thing is the “eternal summer” phenomena in Usenet in olden times)

In any case, worrying about the nonexistent risk of swimming in a recreational pool is counter-productive — casual swimmers will be turned off by the experienced ones.