Alright, my father did this hike two times already, and when we walked back to our car at the end of the day, we saw a guy running down and running up the trail just for (training) fun. This hike is beautiful, but very exhausting and hot in the sun. On the way down, you lose exactly the same 1300 feet (ca. 400 m) elevation that you have to climb on your way back. But it is not only about the exercise and the solemnity in the lava desert, but also about a place of great historic and cultural significance that can only be accessed by this trail, by kayaking an hour, or (unfortunately) by doing a 100$ boat ride.
As the area down by Kealakekua bay is completely uninhabited by humans, there is comparably much wildlife in the reef at the shore. Here the ancient Hawai'ians had royalty temples and plantations, and here Captain Cook landed in 1779. In contrast to earlier visits which were peaceful (he was even considered god-like because he arrived in the right month and circled the island in the right direction on his first voyage), this last visit created tensions (the Hawai'ians had finally learned that he was not god-like, but just a visitor that needed water and food in exchange for knifes and nails). There was a dispute about stolen pigs (by Cooks men) and nails (by the Hawai'ians), shots were fired, and finally he was slain at the beach. Much later a little monument is erected there, and if you look very closely you find a small cross in a lava stone at the very place where it happened (see photo).
What I liked most about the snorkeling here was that you had many of these swarms of fifty vivid yellow fishes, really close as the GoPro picture shows (and even closer feeling through the diving mask). At other spots, especially where the reef vanished in the deep, many black triggerfish swam around near the water surface.