Kahaluu Bay, five miles south of Kailua-Kona along Alii Drive, is the most reliable snorkelling beach in West Hawaii. The bay is small, shallow, and partly enclosed by an ancient stone breakwater built by Native Hawaiians, which damps the ocean swell and creates a calm lagoon almost regardless of conditions outside.
The reef inside the bay supports a large resident population of green sea turtles, parrotfish, surgeonfish, and yellow tangs — and the proximity to shore makes them easy to see. A volunteer programme called Reef Teach has reef guides on the beach most days explaining how to snorkel without damaging the coral or harassing the turtles. The beach itself is small (a strip of black sand and lava rock); arrive early for parking, and avoid swimming on big-surf days when the seaward current can be strong.