The Ribbon Reefs - Great Barrier Reef

From space, the only biological community visible on Earth is a string of coral reefs, the longest in the world: the Great Barrier Reef embracing the northern Queensland coast of Australia. This labyrinth of green and blue, broken up by sand cays and forested islands, stretches 1,600 miles, making it the world's most-complex and extensive reef system. This ecosystem supports diversity that ranges from giant clams with cerulean and violet fleshy interiors to dugongs and nine seahorse species. Visit during winter and you will likely swim with minke whales.

Although there are a few exceptionally good sites accessible by day boats from Cairns and the Whitsunday Islands, the best way to sample some of the greatest dives is via live-aboard. Mike Ball's Spoilsport is one of the pioneers of this area, having led tours here for nearly 20 years.

Located to the north of Cairns, the Ribbon Reefs comprise the northern stretch — divided into 10 coral ramparts — of the Great Barrier Reef, from Cooktown to the eastern Torres Strait. Here lay the jewel-of-the-crown dive sites, including Pixie Pinnacle, Lighthouse Bommie, Steve's Bommie, Temple of Doom and Dynamite Pass. Bommie is an Australian term for a detached coral outcrop that rises from the seabed to near the surface. The Ribbon Reef formations include beds of huge plate corals, isolated pinnacles shrouded in curtains of fish, walls, drift-diving-only channels, caves, canyons and shallow coral gardens.

The signature site for the GBR is undisputedly Cod Hole on the northern end of Ribbon Reef No. 10. As divers plunge in, these fish appear for a handout. But the cod have to be quick: Leopard moray eels and large Napoleon wrasse also line up. Now accustomed to the feedings, the cod are easily approachable and not shy around cameras.

Quick Guide Mike Ball Dive Expeditions' Spoilsport is a 110-foot, twin-hull luxury yacht with a 36-foot beam. The well-appointed vessel caters to 28 divers in 13 cabins, served by a crew of 11. Nitrox and rebreather support are available upon advance request.