When I was a kid there was Raging Waters and Magic Waters. And I think there were some waterslides at the Classic skating place in Midvale or Sandy. And there was Laguna Beach.
But now—despite the population probably more than doubling over the last 30 years—there is the Splash Summit in Provo, Laguna Beach still, and the Cowabunga place in Draper that charges over $20/kid.