Ahihi-Kinau Natural Preserve is another terrific place; it requires more effort to reach it, but it's worth it, because it's home to Maui's tropical marine life at its best. You can't miss in Ahihi Bay, a 2,000-acre state natural area reserve in the lee of Cape Kinau, on Maui's rugged south coast, where Haleakala spilled red-hot lava that ran to the sea in 1790. Fishing is strictly kapu here, and the fish know it; they're everywhere in this series of rocky coves and black-lava tide pools. The black, barren, lunarlike land stands in stark contrast to the green-blue water.
After you snorkel, check out La Pérouse Bay on the south side of Cape Kinau, where the French admiral La Pérouse became the first European to set foot on Maui. A lava-rock pyramid known as Pérouse Monument marks the spot. At Cape Kinau, there are three four-wheel-drive trails that lead across the lava flow; take the shortest one, nearest La Pérouse Bay. If you have a standard car, drive as far as you can, park, and walk the remainder of the way All you need are a mask, a snorkel, fins, and some basic swimming skills. Floating over underwater worlds through colorful clouds of tropical fish is like a dream. In many places, all you have to do is wade into the water and look down.