The Great Barrier Reef is, of course, one of Australia's biggest attractions. This is a "mecca" for scuba divers and the marine environment attracts hundreds of thousands of visitors every year. Actually it is not a single unbroken coral reef, but a series of "small" barriers that extend for nearly 1000 km off the coast of Queensland. Given its size, there are many points from which to access it. Many people choose to visit the barrier near Cairns, since they're closer to large population centers. But it is also possible to visit observation decks of the barrier near the Whitsundays, like Reefworld at Hardy Reef. These sites make an underwater experience accessible to non-divers that they could otherwise hardly have. The platforms are anchored in front of the reef and have fixed observation posts (with explanations of local wildlife) and often a small submarine that can move around the reef in comfort. Besides it is also possible to dive or snorkel in group outings. We visited the platform from Hamilton Island (about a 2 hour sail in rough seas), but it can also be visited from the mainland coast (Arlie Beach, for example). Just remember that it is offshore and dizziness is more than a possibility. If the sea is choppy I really don't recommend the experience, since visibility will be quite disappointing.