The 2nd part of my hike on the Na Pali Coast consisted of going 2 more miles from the beach up a canyon to this 300′ waterfall, upon which I swam in the pretty cold water over to the rock face and got under the falls. I worried a bit about a rock or branch coming over the falls, but figured the chances were slight. A bunch of young people we doing the same.
By the time I got back to my car, I’d covered 8 miles (round trip) in 5-1/2 hours. It’s about 11 miles to the end of the trail (you can’t get through to the road north of Waimea (or at least it’s very difficult), so you have to backtrack, and this means spending at least one night camping. I talked to a guy who went in for 2 days and ended up staying 11.