Oahu's diving may not be the islands' best, but it has enough epic descents to keep scuba connoisseurs smiling. The favorite tends to be the YO-257 navy oiler, which Atlantis Submarines sank as an artificial reef within sight of Diamond Head (yo257.com). The hull rests 100 feet down on the sandy bottom, but its resident turtles prefer to lounge on the main deck at 75 feet. Keep an eye out for spotted eagle rays too. Also off the southern coast, corals blanket the volcanic formations and lava tubes at ‘Ewa Pinnacles. To the north, blow some bubbles at Shark's Cove, one of the world's top snorkeling and shore-diving sites in summer.