Bora Bora, French Polynesia

The island's barrier reef encircles 10 square miles of calm flats, home to manta rays and 500 fish species, offering a biodiversity bounty unmatched by most French Polynesian isles. Prices are steep, but the experience—sunrise from a glass floor over a coral garden—justifies the splurge for travelers seeking the definition of paradise, if you can stomach the premium.