After the second morning at Seaworld, we got the bus over to their Sister waterpark Aquatica. That way you only pay 1 parking fee!
It was fabulous. More wave machines, but there were downtimes too. Unfortunately I'd run my battery down taking pics at Seaworld (Shamu Show part 2), but it also had some great rides and features, and also the free life preservers.
One thrill was anything but a lazy river, Roas Rapids. The artificial current propels you all around the park. Whilst it was fab, I went with Scarlett, in a life vest, but I was still concerned when she went a head of me. Of course she loved it, she has been quite the thrill seeker this trip!
As it comes with your ticket it's well worth using on a blistering hot day. It hit 91 the afternoon we were there.
We only did 2 water parks, this and Typhoon Lagoon, which was part of Disney. Both were excellent but at a push I'd say the the Typhoon Lagoon felt a little dated in comparison. Having said that, it was the only park we visited that didn't ask for a parking fee, so maybe they bear that in mind?