High Park Pool is a great outdoor pool, with a clean modern look and a fair amount of swimming options considering its moderate size. There's a regular pool, but also a kids' pool, with a huge slide. It's not the best place to go for laps, because the adult swim times are short, and it takes them a while to set up the lanes.
There's free parking in High Park near the pool, but not too much, so even at non-peak times, you may have to circle around a bit. Even if you find a good spot, you might (as happened once to me) get boxed in by someone who's double-parked. Better to walk or bike if you can.