It's a little bit off the Hana Highway and we started to wonder if we made a wrong turn, but don't give up. It will be there if you follow the signs. There is a blowhole, but it is not always active (was not when we were there) so you may not get to see that. The views of the ocean meeting the lava rock shore are really beautiful, and worth the time to take in. There is also a lava tube that you can walk into, and watching the waves roll into the end of the tube is pretty unique.
In another area of the park there is a black sand beach, and I was struck by the approach to the beach. While you are still far from the beach the black lava rocks are quite large, but the closer you get to the beach the smaller the rocks get, until they are just tiny black pebbles on the beach itself . . . the action of the ocean over time. There were some people wading on the beach, but the waves break pretty hard there so you would have to be very aware while wading.
There are also bathroom facilities in the park, which can be hard to find on the Road to Hana, so this was welcome. This is a great place to stop for a picnic lunch if that fits your schedule. The trails walking around the park are easy to negotiate, and the only stairs I recall were going down to the black sand beach. There is no fee to enter the park, which was also nice.
Overall, a great visit, and we would definitely stop here again.