See all the best Great Barrier Reef tours from Cairns, Port Douglas, the Whitsundays, Fraser Island and Magnetic Island. Great Barrier Reef dive Tours and Cairns snorkel Tours. Book a Sailing Tour in the Whitsunday Islands or a Liveaboard Dive Trip in Cairns. Swim with Dwarf Minke Whales from Port Douglas, or Dive with Sharks. Take a Scenic Helicopter Flight over the Great Barrier Reef. See all Dive trips from Port Douglas. Instant book online, Live availability.