Waipio Valley
This was a crazy hike in a very cool place. We saw the waterfall at the back of the valley, and talked to some locals who had attempted the trip, so we figured we had enough pointers to get us there.
After the crazy decent on what is apparently the "steepest road in the US (and possibly the world)" according to wikipedia... the trek to the falls takes a turn in to the unknown.
The "trail" is immediately before the stream... and it's tough to tell if it's actually a trail. Things are so overgrown, that you end up almost crawling to get through some parts. Once you hit the "No Tresspassing" signs, you have to back up a bit to find the river crossing. Slippery at best. My wife took off her boots, but I left mine on (mistake) and ended up submerged up to the shins.
The other side of the river is challenging. Very tough to tell where the trail is, and you end up blazing your own for half of it. A machete would have been VERY handy here (which we confirmed later with a Ranger here in WA who grew up there). Bushwacking 101.
After making it half way to the falls, we aborted :(
There is a pool the you have to wade through, and carry your pack above your head. The local said it is probably 5' deep, so my wife would've ended up swimming.
It was disappointing to abort, as we couldn't yet see the falls, but it was definitely a cool experience. Seemed like a scene from 'Lost', as it was very jungle-like, and somewhat spooky in the dense overgrowth.
The locals said that even when they cut through with machetes, it grows back in a couple of days.
I see that others have made it (on here). Will be interesting to see if there are any tips :)