Most visitors to the Great Barrier Reef combine stays on one or more islands with time in Queensland's coastal towns and national parks. With a week or more, you could stay at two very different Barrier Reef island resorts: perhaps at an activities-packed Whitsundays resort and one of the more remote northerly islands, allowing a day or two to travel between them. If you want to resort-hop, opt for the Whitsundays, where island resorts lie in relatively close proximity and are well serviced by water and air transport.
If You Have 1 Day
Take a boat from Cairns or Port Douglas to a pontoon on the outer reef for a day on the water. A helicopter flight back to the mainland will give you an exhilarating aerial view of the reef and its islands. Alternatively, catch an early boat from Cairns to Fitzroy Island or from Shute Harbour to Daydream Island. Spend a couple of hours snorkeling, take a walk around, then relax on a quiet beach or in the resort bar.
If You Have 3 Days
Pick one island that offers a variety of aquatic and land-based activities and attractions—flora and fauna, beaches and dive sites, sports and relaxation facilities, resort-style nightlife—and give yourself a taste of everything.
If You Have 7 or More Days
Planning to spend a full week on an island probably means you're a serious diver, a serious lounger, or both. Keen to scuba dive the reef? Hop on one of the Lizard Island—Port Douglas live-aboards for a multiday dive trip, then recuperate on an island that has fringing coral, such as Lizard Island. Or stay at any Whitsundays resort —most have fringing reefs and can arrange dive-boat excursions out to Barrier Reef pontoons. Live-aboard trips can be surprisingly affordable—typically, they run from two to 10 days. Beach lovers might prefer to focus on exploring one or two of the islands with outstanding beaches and hiking terrain, such as Orpheus, Lizard, or Hayman.