I did not grow up in the Issaquah, Washington area, but this classic commercial for Waterworks looks a lot like the regional commercials for water parks that I saw growing up in New Jersey. While I am sure Waterworks was not as dangerous, the images and tone reminds me a lot of the infamous Action Park.
A quick search online did not reveal any of the lawsuits or reported injuries that I would have guessed would have plagued a 1980s water park, but I did find this article about them temporarily closing Waterworks because of “Hot-Tub Itch” in 1984.
Here is a commercial from 1985.
(the Waterworks Park in Redding, CA still seems to be open)
And here is some footage shot by a visitor to the park in 1986