The four of us did the first few miles of the Kalalau trail on the Napali coast. My son and I did a day hike to Hanakapiai falls. It is supposed to be 8 miles round trip but my Fitbit said a hair over 10. Some pics below -
You need a permit to hike the full 11 miles (22 miles round trip) including an exposed cliff section called crawlers ledge. Son says a solid maybe’
You are of course subject to the weather. We were lucky - a bit of mud but that was it. The hike is in rain forest and exposed arid areas. During the miles we drank 4 liters each.
Most fun hike I have done. We swam in the falls for about 45 minutes before turning around. 6 hours 30 minutes round trip and over 5,000 in elevation change (lots of up and down but you don’t get too high up).