Pool cleaning lasts until 6:45 or so and opens at 7. Was just me and one other guest swimming laps until around 7:30. We shared the pool with a flock of ducks that kept a safe distance from us.
Pool typically closes at 11, but the cast members here don't seem to care if you stay in until 3am or later. No need to rush the parks to make sure you get back before the pool closes!
If you get a drink at the bar, add a 151 floater. They're only $1.75 extra, and without it the drinks are weak at best. With it, they're actually worth the money.