Kick your snorkeling up a notch with a visit to a partially submerged volcanic crater. Boats leave daily from Makena Beach and Lahaina Harbor (among other places) for the ancient atoll of Molokini, 2.5 miles off the south coast of Maui. Excursions take you straight to waters teeming with marine life that offer a visibility of up to 150 feet and little ocean swell. These splendid conditions perfectly showcase yellow tang, parrotfish, black triggerfish, bluefin trevally, and even moray eels. Hop on an early-morning boat for the best chance of calmer seas and bigger sea creatures, such as octopus and eagle rays. Bring along snacks, sunblock, and—for those who run cold—perhaps a rash guard or thin wet suit, especially in winter.