Lulumahu Falls is technically on private government property (definitely a perk), but the reservoir and its facilities have been abandoned for some time, and this spot is getting more and more popular. It's a sweet hike that has you going through a bunch of different types of terrain and is sort of a maze to find. In other words, a great hike.
1. There's a parking area off the Old Pali Road (if you've gotten to the overlook, you've gone too far) where it meets the Pali Highway. It's basically a reddish dirt lot on a decently steep incline. You'll likely see a Board of Water Supply gate. If you do, you're in the right spot.
2. Most other guides talk about not entering at the mailbox and wooden sign (which is right where you parked), and instead walking a bit further down and going through a large hole in the fence a little bit further down. I say, eff that. That way takes you immediately to wide paths and power lines. Nope. If you go at the mailbox and the wooden sign, you walk into the bamboo forest and have to MacGuyver your way through (well, sort of. You'll see a path, it just won't be something you'd drive a Subaru down).
3. Walk into the forest. Think about how you're touching panda food. When you hit a fork, turn right.
4. At the next fork, take a left. You'll be following an old riverbed (or just a riverbed, depending on the recent amount of rainfall).
5. That'll open up to a gravel road. Take that to the left.
6. You'll see a large outhouse-looking building covered in graffiti in front of you. Go to its left and you'll see a set of cement stairs. Take 'em. You're going back into that sweet, sweet bamboo forest.
7. You're gonna exit the forest and see a path in front of you. Take it, and when it splits, go to your left.
8. You're gonna see an open clearing about 10 seconds before you hit it. Get excited. Then walk into it, and get more excited. Also, take note where you are. You're gonna need to know how to get back (aka between the tall tree and the stump).
9. There's a hill to your right (pictured above). Walk up it. Hope it's not muddy, because that's all you can do. Once you walk up it, here's the view to your left:
10. You're gonna wanna follow all the people and go this direction. Do that for a bit, take some pictures of the reservoir (below), but then turn around because that's not the direction you want to go. Go to the right.
11. Follow this path (the one pictured above) until you see two sets of stairs. Take the ones on your left. Also, if you see a graffiti wall, great! I only saw it on the way back. Whoops.
12. There will then be a giant, square hole in the ground. There's a fence around it and several openings. Choose whichever opening you want, but work your way toward another set of stairs across from you.
13. This leads you to a narrow cemented path that looks like the edge of a dam. You have to walk along it to get to the other side. It looks scarier than it really is.
14. Now it's stone time. You're just gonna be crossing the stream, jumping over rocks, and in general working your way upstream (and getting your feet wet. But don't worry; it's so humid, you won't mind). We took the path on the right up and on the left down. They both had their obstacles. As long as you stick near the water (and have a decent pair of shoes (though I did see a guy going at it barefoot)), you'll be good.
15. After half a mile or so, set your eyes on the prize. Get in the damn water because your feet are already wet, anyway. Dunk yourself underneath the falls and sit for a second to thank Mother Nature for being awesome. There's a small wading pool at the bottom and plenty of large rocks to practice your Ariel impression.
"Look at this stuff, isn't it neat..."