Went down a rabbit hole after exploring that park, and then remembering the three outdoor waterslides that existed in Austin in the 70s and 80s. Flowmotion / Ski and Skate was located on S Congress and was my go-to. They eventually shut it down because of unpaid taxes and other lawsuits, so they sold it off to make room for another Austin institution (Expose Mens Club). Wet Willie's was on the big hill off Ben White where St Davids Hospital now sits. That place was literally a death trap and at least 2 people died there. Surprising, I know; what could go wrong by putting a few curving concrete half pipes on top of a hill, wetting them down, and shoving a bunch of drunk people down them? Aqua Thrill Ride was off south I-35 but I never went there.
I went to Ski and Skate a bunch but every time I got hurt, either from sliding across the concrete curves, getting grassburns from flying out of the concrete half pipe, or getting paint chips lodged in my skin. they also had the "grass skiiing" hill which was basically strapping kids to busted up rollerblades and shoving them down a hill full of grass burrs. I remember going to the doctor to get a massive paint chip removed from underneath my big toe, courtesy of one of the waterslides, causing my toenail to eventually come off which was all very exciting as a 12 year old.
Also on a related note, nothing beat the crazy "ride" at Schlitterbahn back in the day where you'd walk up to the top of a house, hop on a greased up tray, slide down a two-story track across from your competitor, and then hit a pool of open water with no guardrails and go skimming like a stone to God know where. Of course the unwritten goal was to pull up the tray so as to turn and smash into your competitor, which often happened whether you meant to or not. They changed it all up later, so that you have a lame track you stay in all the way to the end. Anyone that wasn't around in the 80s really missed out on waterparks before lawyers.