Who invented waterslides? And when were they invented?

I really don't think this is an easy to answer question. Waterslides are slides with water as an additional "feature" to normal slides like on playgrounds. Also in the history of mankind, slides were a tool for building things up, not for fun purposes. So you have to ask, who uses slides the first time for fun I researched about this topic a long time ago, but I could not find anything about the inventor of slides for fun purposes.