Punalau Falls is one of the lesser-known waterfalls along the popular Road to Hana. One of the reasons is because it can't be seen from the road. And another one is because it takes a short, but slippery hike to get to it.
From the turnout, about a quarter mile past mile marker 13, it's about a 15-minute hike. You'll have to walk on the slippery and partially submerged rocks of Punalau Stream because there is no trail. The stream may be a mere trickle on some days, but if it has recently rained or it is currently raining (or you notice a dark cloud upslope) it is best to avoid hiking to the waterfall because of the danger of flash floods and falling rocks. There is no escape in this narrow gulch if a flash flood is on its way.
CAUTION: As with all freshwater streams and waterfalls in Hawaii, Leptospirosis bacteria may be present in the water. Do not drink the water and keep water out of open wounds (including small scratches) and eyes.