I've been around a long time and I went to a water slide park right across the street from Disneyland back around 1980. It was located on the other side of Ball close to the Anaheim Sheraton called the "Wild Wild Wet". As I remember, it was pretty fun for an old school type waterslide park, the slides were concrete!
So, its been done already!
Here is a link to an article about the park:
The Wild Wild Wet in Anaheim ~ Orange County Memories