Mananole Falls (or Mana-nole Falls) is a light-flowing tall waterfall (supposedly 1000ft tall) deep in the Waihe'e Valley of West Maui.
I don't think you can get close to the waterfall, but you can see it from above along the Waihe'e Ridge Trail and from below along the Waihe'e Valley Trail (as you can see from the photos on this page).
Both times I have noticed this waterfall from terra firma were on our visit to Maui in September 2003. The first one was from the Waihe'e Ridge Trail near the Waihe'e Valley Overlook. The second one was along the Waihe'e Valley Trail quite far into the hike before the Ali'ele Falls.
More recently in 2007, we did a chopper tour of West Maui and Molokai, and in that particular trip, we flew into Waihe'e Valley where we got to see this waterfall from closer up.