About an hour and a half south of Rotoiti. I made a snap decision to follow a narrow little side track which got alarmingly narrower and littler and pot-holier before I decided that it was not a wise idea to take the rental car any further. The falls were just around the corner.
I've heard that there are somewhere near the Maruia river wild hot springs. I haven't seen them, much less swum in them but I'd like to some day.