Whether young or old, triathlete or couch potato, everyone appreciates the island's most easy-to-access (and admittedly busy) snorkeling spot. Protected by an ancient breakwater (which, according to legend, was built by the menehune, or 'little people'), the bay is usually pleasantly calm and shallow. You'll spot tropical fish, but beware shallow stretches where you might bump on rocks. The lifeguard-staffed park has outdoor showers, restrooms, drinking water, snorkel rentals and picnic tables. Water can sometimes get cloudy later in the day.
Come early; the parking lot often fills by 10am. Kahaluʻu can be too popular for its own good, with snorkelers literally bumping into one another. The salt-and-pepper beach (composed of lava and coral sand) is often a mass of sociable humanity. Treading lightly is important: follow coral-reef etiquette. By law, you must stay at least 50yd from all sea turtles in the water (20ft on land).
When the surf's up (and it can rage here), expert surfers challenge the offshore waves and avoid strong rip currents on the bay's north side near the church. When conditions are mellow, beginners can learn to surf or stand-up paddleboard.