The Y closes their pool in Cranston at the drop of a hat. Today for example it's closed to repair the pool deck. Then there's swim meets. Then there's family hour. So actually there's really only early AM blocks of pool time, sometimes afternoon too, but the pool there generally is off limits around 6pm while the rest of the YMCA is open until 9pm.

Edit: I forgot there is an 8:00-8:45pm swim block. Again, you'd have to go to your local YMCA and ask for the pool schedule, or maybe check their website for hours.