Pololu valley is the most northern of the valleys that are carved into the Kohala volcano in the Kohala region on the Big Island.
The hike starts with spectacular views of the valley and the steep cliffs that end in the ocean and are worth a trip on their own, but the real thing to do here is hiking to the black sand beach at the valley floor.
The hike starts at the Pololū Valley overlook and is marked by an extensive array of “danger” signs. Hike down the wide, rocky trail to the valley floor 1/4 mile from the trailhead. Not a horribly difficult hike down, but can be slippery if it has rained recently. Once on the valley floor, the flora changes abruptly into large ironwood trees just behind the beach. There is a river near the beginning of the beach that you may have to cross (depending on the recent weather - this may be dry). If it is flowing heavily - DO NOT CROSS. This river is fed by agricultural runoff, so carefully consider how you treat this water before drinking.
The Pololū Valley beach is mostly made up of moderately-sized polished lava rocks. The water here is notoriously dangerous and should only be attempted by very experienced swimmers and surfers. There is no lifeguard.
When you're ready, climb 300' back to the trailhead. The climb back up is definitely more difficult than coming down to the beach.
Hiking boots and a hiking stick are really helpful (if you don't have one, there are a number of branches available to use). Bring lots of water and maybe something to snack on.
Please NOTE: This location requires a travel fee. It is an hour and a half from Kona and two and a half hours from Hilo.