Rosemarie,
My whole family did the slide on Kauai in 1977. We were told it was actually used in Elvis' Blue Hawaii film. The waterfall slide was all natural before the Blue Hawaii film, but they added the cement to make it easier on the a** for filming....still you had to wear cut off jeans because the cement was pretty rough.
Never heard about it being used in South Pacific.
You did have to ask locals for directions and it was a short hike in. When we were there, there was a mix of local Hawaiian kids and a couple visitor like our family. We had fun talking to the kids and the waterfall was a BLAST! Yes, quite a drop into the natural pool below the falls. There was also a great "Tarzan" rope swing in a tree that you could also drop in from!
Years later I heard that local law enforcement had fenced and closed down the falls due to overuse and drug traffic problems.
I've never heard anything further about it.
Good luck. I hope you get to enjoy as much as we did!