The Great Barrier Reef, the world’s largest and best-known dive destination, is freighted with divers’ expectations. This series of fringing, platform and barrier reefs spanning 1,400 miles promises 400 species of corals and 2,000 species of fish. It’s also the cruising ground of minke whales in June and July, while year-round, pelagics such as silvertip and whitetip reef sharks make appearances on most dives. Sites just outside Cairns provide a sample of what lies beyond, but to truly tap into the awe factor of this dense ecosystem, you have to commit to a live-aboard.

Itinerary

Day 1 -- Dine on your own in Cairns, then make your way to Trinity Wharf at 6 p.m. for boarding. Check-in follows a champagne toast. Overnight trip to (1) Ribbon Reef 10.

Day 2 -- Get your bearings with two dives at (2) Challenger Bay, home to cuttlefish and spotfin lionfish. Dives three and four are at (3) Cod Hole, where the resident giant cod make ideal photography subjects. Overnight to (4) Osprey Reef, weather permitting.

Day 3 & 4 -- Osprey Reef. At current-swept wall dives such as Round the Bend and Halfway, watch for hammerheads, chevron barracuda, sharks and other predators attracted to fast-moving water. At the shark feed at North Hole, become mesmerized by the competition for tethered tuna heads between the potato cod, whitetip reef sharks and silvertip sharks. Overnight to (5) Lizard Island.

Day 5 -- Half-week guests depart while weeklong guests hike among the pandamus trees. After new guests board, it’s back to Cod Hole and Challenger Bay.

Day 6 -- At (6) Lighthouse Bommie schools of trevally, batfish and snapper patrol the blue, while Olive Ridley turtles, stonefish and sea snakes claim resident status on the pinnacle. At (7) Pixie Garden, think small and scout for nudibranchs and leaf scorpionfish. Overnight to (8) Ribbon Reef 3.

Day 7 -- (9) Steve’s Bommie, just a half mile from Ribbon Reef 3, offers a wealth of color, from the school of snapper blanketing the reef to the anemonefish holding court in anemones and the array of nudibranchs inching along the corals. Finish the day diving at Ribbon Reef 3. Overnight back to Trinity Wharf.

Day 8 -- Depart.

Departing from Cairns, Mike Ball’s Spoilsport threads along the Barrier Reef to reach sites so remote that only one or two boats dot the uninterrupted panorama of glittering turquoise and cobalt. It’s here in the Coral Sea that the reefs and their inhabitants, untouched by water runoff or development, can swell to epic proportions and numbers. Tucked within lagoons of the various Ribbon Reefs, many dive sites shelter fat swathes of branching and plate corals in neon blues, pinks, yellows and other vibrant hues. Life in the form of regal angelfish, pink anemonefish, clown triggerfish, blue-green damselfish and other eye-catching species clutter the reef, while unicornfish and bumphead parrotfish cruise nearby. One of the most memorable dives, Osprey Reef’s Round the Bend, aka Fast Eddie’s, requires use of dinghies to deliver divers to the heart of the action. Drop into the swift current just where the reef wall juts in at almost a right angle to a sandy cove. Stay low to the wall and wait for the curtains of snapper and goatfish to part, revealing tuna, giant trevally and silvertip sharks. Then fin over to the shallows, where nearly a dozen whitetip reef sharks sleep on the sand. To ensure a breezy week of maximum diving and ample downtime for as many as 29 guests, Spoilsport’s nine crew and three volunteers vibrate behind the scenes on a timely, seamless schedule. They ensure tanks are always full and a meal or snack is just minutes away. Serving up variety, the chef prepares a mix of Australian, Thai, Mexican and continental fare to keep palates satisfied and energy levels high. In between dining and diving, visitors can spread out in sun or shade on the two lounging decks, or on the sofas in the air-conditioned cabin with its library, entertainment system and computer. There, the onboard photographer and nature expert host fish and invertebrate talks that cater to guests’ hopes of developing stronger understandings of the marine life that makes the Great Barrier Reef the world’s most expansive underwater wonder.

Need to Know

Travel Tip -- An hour’s drive from Cairns, the Rainforest Habitat in Port Douglas showcases much of the country’s wildlife and ecosystems, ranging from dry savannah to rainforests, coastal areas and tablelands. Arrive in time for breakfast with the parrots, parakeets and other birds that help eat your Corn Flakes. Don’t forget a camera, as you’ll also get the chance to feed kangaroos.

When to Go -- Minke whales migrate off the coast in June and July, making sightings almost inevitable at sites such as Lighthouse Bommie. Dive Conditions -- Water temperatures can climb to 85°F in January and February and dip to 73°F in August.

Getting There -- Qantas flies to Cairns (CNS) from Los Angeles, with most flights routed through Brisbane.

More Info -- www.mikeball.com

If the Boat Fits

Two other live-aboards travel similar itineraries departing from Cairns. Along with the Mike Ball, these two also offer three- and four-day journeys, giving the option of diving either half of the safari.

Spirit of Freedom Built in 1992, this 120-foot-long vessel serves a maximum of 26 passengers in 13 cabins. The boat also carries paddle skis, wave skis and a wind surfer. Your cruise on the Spirit of Freedom ends (or begins) with a low-level flight over the reefs between Cairns and Lizard Island for a bird’s-eye view of some of the world’s best dive spots. Prices start at $2,675 per person for the quad-share cabin. www.spiritoffreedom.com.au

TAKA A smaller boat at 100 feet long, the Taka can offer slightly more affordable rates — $2,460 for those who wish to share a cabin with three other passengers. The boat carries a maximum of 30 passengers in 13 cabins, served by a crew of 11. If you’re really looking for a deal and will be in Australia anyway, they occasionally offer standby spots on the boat at significant discounts. www.takadive.com