It may not be what you imagined, but this is the place I mentioned in my previous post, Waingaro Hot Springs. It is all naturally hot-springs fed, but it is treated so that you can swim and splash and not worry about contracting some strange diseases. There are 3 pools, one for kiddies, one for swimming and one for relaxing (that's the hottest one).
This is a quaint little place that reminds me of a scene out of the 60's or 70's. Kinda like 'Dirty Dancing' with water!