I can't tell you much about the pool at Mem Gym [I'm afraid of public pools + my hairdye], but if you cultivate a friend that works there or goes to school there [Bill pops to mind and might be able to give you more info], you can often go as a guest. I used to do that in the early 90's.

We don't have a good Y here, IMO, because we're too goddamn yuppified.
However, if you go to Meade Ave's pool, they have adult swim. It isn't open in the winter, though.

I'll see what else I can find out for you from folks around town if you like! :)