My personal theory about why so many excellent reviews is that this small beach is fairly near Kona, just south. It's a shallow bay, so good for first time snorkelers. Semi-difficult entry to the water, you have to pick your way through a narrow sand channel through the lava to get to open water. You will probably be barefoot, so be careful. But, its pretty protected, so there is only mild current and mild swells - good for youngsters or those who aren't very confident in the water. The reef is a little beat up, but there are plenty of fish, and most days there are turtles. A few sandy areas and some grass to lounge in. This washer first in the masks and fins in a few years, and we all agreed this was a good place to reacquaint ourselves with snorkeling for this trip. Much better snorkeling at Beach 69 Waialea in Puako up the coast, and at the beach at Mauna Kea hotel (there is public access, ask at the gate). Also, better snorkeling at Two-step at City of Refuge. Entry to the water is only for the reasonably bold there, though. My nieces thought the best thing about Kahulu'u was the shave ice truck. The more snorkeling we did at other beaches, the more I began to think they were right.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.