If you snorkel only once, make it at Olowalu, home to Maui's most diverse marine populations. Slap on some reef-friendly sunscreen and explore more than 100 acres of some of the healthiest coral structures in Hawaii. Watch manta rays and green sea turtles rock up to cleaning stations, or peer inside a nursery for blacktip sharks among the 500-year-old coral formations. Less of a swimmer? Then try a stable wide-bottomed ocean kayak for a different perspective. The tiny town also contains the island's best petroglyphs, as well as a haunted past: Here, trader Simon Metcalfe massacred more than a hundred innocent Hawaiians in 1790. This outrage spurred King Kamehameha I to defeat his neighbors, using Western weapons and tactics; after 20 years, he succeeded in unifying all Hawaii.