Book excerpt: Australia's Great Barrier Reef is the only living structure on Earth visible from the moon; at 348,700 square kilometers (238,899 square miles), it's bigger than the United Kingdom. It stretches over 2,000 kilometers (1,250 miles) and is home to some 1,500 kinds of fish, 400 species of corals, 4,000 kinds of clams and snails, and who knows how many sponges, worms, starfish, and sea urchins. In short, the Great Barrier Reef is the Eighth Wonder of the World. Frommer's Portable Australia's Great Barrier Reef gives you the lowdown on some of the best sites to snorkel and dive this magnificent piece of nature and tips on how to make the most of your experience. We tell you about the top dive and snorkel sites, as well as some remote beauties that are rarely explored by travelers. We walk you through everything from how to choose a gateway to the Reef to how to pick a dive course. We recommend the best boats for exploring the Reef, from day-trip vessels to dedicated live-aboard dive boats. We tell you about some of the wonderful creatures you will see (and the few scary ones to avoid!). We recommend places to stay, from inexpensive B&B's to glamorous Great Barrier Reef island resorts. And recognizing that even die-hard snorkelers and divers want to take a break from fishes once in a while, we cover the best stuff to do on dry land, such as taking a four-wheel drive safari into World Heritage-listed rain forest or visiting a to turtle rookery.