POPULATION: 3,300
SIZE: A ring of coral never more than a mile wide and often only several yards across
TAGS: Ten-pound bonefish, unreal diving, fresh Pacific mahi-mahi

Make the trip to Rangiroa to be submerged—very few of the island’s activities occur on land. Its 50-mile-long-by-20-mile-wide lagoon has accumulated a massive shelf of finely ground coral sand in the remote southeastern tip, creating miles of pink-tinged sand flats. Here six-to-10-pound bonefish cruise solo or in small groups, easily visible against the sandy bottom, and many of them have never been cast to. To find them, acquaint yourself with the expert local guides hired by Tahiti Expeditions (day trips, $460). Almost anywhere you plunge into Rangi’s water, you’ll find world-class snorkeling and diving conditions. Go with Top Dive, whose staff has been exploring these depths for years (one-tank dive, $88). You’ll be surrounded by blacktip reef sharks, sometimes hundreds in a day, and they’re completely uninterested in you. Or snorkel the narrow Tupita Pass between the lagoon and the Pacific Ocean during an incoming tide, drifting along in a seven-knot current with a mind-blowing array of marine life. Stay at the swanky, refurbished Hotel Kia Ora resort (from $625) or the simple water-front Tevahine Dream guesthouse (from $125) near the sleepy village of Avatoru. Dinner is fresh mahi-mahi with vanilla sauce at Le Magic Kaikai.

ACCESS: Take a 90-minute Air Tahiti flight from Papeete.