What is one thing not to miss on Maui?

If you can only do one thing on Maui, make it a snorkeling trip to Molokini Crater. This partially submerged volcanic caldera sits three miles offshore and hosts over 250 species of fish in water with visibility exceeding 150 feet. Pride of Maui ($115–241) and Four Winds ($80–180) are the leading operators, departing from Maalaea Harbor most mornings. The second non-negotiable is the Road to Hana — 52 miles of coastline with waterfalls, bamboo forests, and black sand beaches, best experienced with Valley Isle Excursions ($216–280) if you don't want to drive. A helicopter tour over Haleakala crater and the West Maui Mountains from Blue Hawaiian or Maverick ($229–480) rounds out the essential Maui experiences. Any one of these is worth the trip.