This is probably the easiest hike we did on Oahu. It is relatively short (2 hours total) and the path is well traveled. It will be moist once you get higher up the trail. Wear gold shoes, and dress for some rain. It feels like you're in the rainforest!
Beautiful hike. Awesome views at the top. Closer to 6 miles than 4.5. This will take most people 5 hours to fully complete. I think we did it in 4:30 and that was moving faster than anyone else we saw on the trail that day.
Definitely do this one on a dry day with at least one dry day before. This would be close to impossible in muddy conditions. We went on a dry day following two prior dry days and the conditions were fine.
As another reviewer wrote, stay close to the stream and the drain pipes and you'll be on the right trail.
Also get there early as there are only about 6 parking spaces.
NOT DOG FRIENDLY!
I loved this hike. I typically go barefoot when I hike and I would recommend this to everyone. It's a mud filled hike so prepare to get dirty and if you aren't wearing the correct shoes you will not be having such a fun time. Beautiful view from the top, three waterfalls and a switch back route. Enjoy.