By Steve Chapple
Photography by Stephen Frink

Anticipation builds like a public hanging. Twelve of us are seated in full scuba gear 30 feet underwater, waiting for the sharks off Osprey Reef in the Coral Sea. It's awkward keeping your balance, seated with fins down, neoprened backs straight, nestled into the natural indentations of the little amphitheater carved out of the great wall. ("Careful not to sit on a stonefish," the dive director has cautioned.) The wall slopes, then drops to very deep water, perhaps 3,000 feet below. A bommie, which is the Aussie word for pinnacle, rises right in front of us like a sharky stage, flat on top, with a small separation of open water, 50 feet at the most, between us and the heavy, to-be-baited chain tied to a buoy at the surface. There is no shark cage. That's the old way, and besides this is Australia. They like to get up-close and personal Down Under, give the American tourists a bit of a fright, and some value for their sinking dollar.

At first, nothing more than a hyper-alert school of redback bass swims around the chain. A white-tip reef shark ambles in, and then another. The divemaster, very briskly, lards the chain with tuna heads. At that moment, my attention focused offstage as more redbacks join in, I hear a loud crunch! I snap back to face the chain. These sharks did not come in on little cat feet. One second and the orchestra of redbacks is warming up, the next a dozen sharks thrash about, tossing their heads back and forth, ripping away the tuna bait. (The point was made at orientation that only elements of their natural diet may be proffered to the performers.) The bigger, six-foot gray reef sharks with their diamondback-shaped heads shove away the smaller white-tips-and they aren't that small-in a jabbing frenzy, no blood, just lots of tuna-head flotsam.

Suddenly, a big, smooth, goofy 300-pound potato cod slips in from nowhere and grabs sloppy seconds. The sharks don't attack it. Perhaps they are afraid. More likely, nobody takes chances among equals. It's like a pack of wolves joined suddenly by a great Saint Bernard. A large Napoleon wrasse fins over the top of the bommie and scarfs its share, too. The writhing mass swirls around the chain maybe four times in unison, and then it's over. Less than a minute. The food is gone. The spooky gray reef sharks sidle off for deeper water. The white-tips sink lazily to the shelf and take up their original patrol. Schools of redbacks and smaller fish search for leftovers, which are few.

Beyond Lizard Island

The way to begin to dive the Great Barrier Reef is not underwater at all, but rather from 1,000 feet up aboard the one-hour flight from the little gateway city of Cairns to Lizard Island, the halfway point of a seven-day trip, where many live-aboards take on passengers. From this window seat, the vast gorgonian fan of islands spreads out: the tiny cays, fringing and ribbon reefs, bommies-those spiraling, stand-alone columns of calcium carbonate and polyp-the languid blue drop-offs, the dark channels and turquoise sandy shallows spotted with the occasional giant potato cod and pencil lines of reef sharks (perhaps only imagined from this high up). There is a vast array of underwater islands, too, teeming at low tide with octopus and crab.

The sheer reach of the Great Barrier Reef is overwhelming: 1,200 miles, 2,500 separate reefs, 400 coral species, 4,000 invertebrates, some 1,500 (and counting) different kinds of fish, from petulant gobies to brooding tiger sharks. It is a watery domain that has become, as of two years ago, perhaps the best, and certainly the largest, marine protected area in the world, an evolving environmental success story in this era of handwringing about global warming. Thirty percent of the GBR has been ruled off-limits to all fishing, the ages-old human pastime that has taken out the sharks and big groupers and larger wrasses, causing to crash, trophically, so many other reefs worldwide.

I begin my structured Aussie dive-ramble from Cairns, aboard Mike Ball's live-aboard catamaran Spoilsport. We steam at 17 knots all night through a stormy sea. Cairns has just experienced its rainiest April on record, and a major cyclone recently left the area. Though ours was an inside passage, dishes and pots rattle and crash in the galley a deck above my cabin like timbales in a calypso band. This does not, in any way, delay the first dive of the morning-7:30 a.m. and don't keep your buddy waiting, mate!

The Australian attitude toward diving, I discover, is much like the Aussie view of dining. Plates are full. You don't have to eat everything, but nobody should leave the country feeling cheated, either. There are five dives a day: 7:30, 10:30, 1:30, 4-dinner!-and then the night dive. The rhythm of live-aboard life is one of nitrogen-filled bliss by day and sleep-through-anything nights, punctuated by multiple warm showers and cool conversation with a pretty cosmopolitan guest list that includes bankers from Hong Kong, firemen and social workers from Canada, a biotech guy from California, the Townsville dive club, who all knew each other from previous jaunts to New Guinea or Sulawesi-wherever!-a Swiss optician, a British doctor, a French engineer, a couple of Sydney kids who mostly watched Austin Powers on the flat screen in the salon, and so on.

We dive Challenger Bay the first morning, then after lunch move to Cod Hole, which we explore by night as well. Then we tuck in and cruise 100 miles northeast to Osprey Reef, in the Coral Sea. The northern half of the voyage offers more pelagics, culminating in our shark feed. The southern half, from Lizard back to Cairns, showcases the calmer Ribbon Reefs, which, because they are less currenty in normal weather, harbor more biodiversity: legions of corals and realms of feather stars, flat worms, nudibranchs, giant clams and quiet little critters. The first dives are shakedown swims. Perhaps I need to jump ahead to Lighthouse Bommie to impart to you the uniquely Aussie dive experience.

It is 6:30 in the morning. Captain Pete boils out of the wheelhouse. He wears blackout sunglasses on his shaved bald bullet head, black and orange board shorts, a neon-blue rash guard and flip-flops.

"Arrgghh! Me hearties!" he shouts, pirate-like. "Weet-Bix!" He proceeds to pluck three of his country's beloved pressed wheat bars from a glass breakfast jar and slather them royally with cream. "This is why Australia is number one in everything: swimming, tennis, cricket! It is a diet of Weet-Bix that has made us strong!"

"Cricket?" I ask.

"Yes, cricket! Number one in everything that matters! Now let's go diving!"

Soon Captain Pete is speechifying from the second-story dive deck. "I go to greet me mates in Davy Jones Locker in the deep! Arrrghh! Arrgghh!" He then performs a perfect back flip-with tank-sporting bright yellow fins and holding his mask with two fingers. It is a giant splash.

Hard to laugh underwater, so I don't. I sink to the bottom with the captain. Lighthouse Bommie rises 90 feet off the sandy bottom. The dive plan is to corkscrew to the top slowly, taking in the sights-the captain immediately wiggles his stubby fingers: "Octo!" Then comes a scattershot of riotous corals, sponges, green anemones defended by orange clownfish, and ascidians or sea squirts-strange, venous purple-and-yellow filter feeders that look like beating human hearts, hence their Latin name Polycarpa aurata. Under a broccoli crown of acropora coral is a slug of a blue lionfish, pennants waving. I hover for a closer look, but not too close. Why do lionfish always look like pissed shoguns? Beside it wriggles a banded pipefish, the pencil-neck geek version of a seahorse, all stretched out and flat. Upward, at 45 feet, sits a flame shell clam hidden in a tiny grotto, though marked today by a lime-green dive light put there by the spotter guide. A filament running along the lip of the open shell oscillates with a line of red and silver light, alien and weird and wondrous. Is its purpose to attract small creatures or to warn predators away? But if you turn the dive light off, the pulse disappears. Does it stay on, in a wavelength we can't see? Then, onward and upward, through clouds of darting pink and yellow and powder-purple anthias.

Creatures of Cod Hole

Time for breakfast. I learn to keep ship's time by the meals, and I am always surprisingly hungry. Breakfast (after the Weet-Bix pre-breakfast) is scrambled eggs, bangers (which are sausage by any other name), delicious fresh-baked toast and apricot jam, pressed cake of hash browns, some kind of limp Aussie ham-bacon and, solely for the native palate, Vegemite, which seems to be a dung-brown brewer's yeast and axle grease concoction, with lemon juice and Angostura bitters thrown in to keep the flies off. It's very endearing if you speak the Queen's English with a nasal twang, and rumored to take the hair off your nipples, too, should you have any hair there, which is why the Queen of England has none, but-

Arrggh, indeed!

Back to the water. There is only one potato cod at the famous Cod Hole, a smallish fish of 100 pounds or so, sequestered in a shallow cave about 25 feet down. The current is strong the first day; it is the night dive that offers the most sport. Dozens of redbacks course about on the surface, smashing baitfish off the dive transom under the big spotlights from the boat.

"This is your chance to play God, should you choose to do so," says the dive director, as he hands out the underwater lights. "Shine your light on a cute butterflyfish, and you may feel a whoosh over your shoulder. That's a big trevally coming in for the kill. They use the dive lights to spot."

As soon as we hit the water, we are picked up by six giant trevally, which are a hump-headed top predator. They follow us around like muscled ghosts, hunting the coral forest with us like a pack of wolves. At one point I shine a light on a sleeping parrotfish. It has spun its mucous cocoon and is hidden under the branching arms of an elkhorn coral, using it like a rabbit might a briar patch. I immediately turn off my light. After a while, I begin to feel sorry for our outriders. One rushes into a cave when I spotlight a tang, but it misses and can't get out. After a few seconds it uses its pectoral fins to delicately back up, like a jammed bus.

I found it sometimes strange to roll out of bed and go diving. My judgment was not always working. It is easy to drop down 90 feet too quickly, without realizing it. Strange to be 90 feet down in a cave before breakfast. The reefs are so endless that I once had a flash, swimming above canyons 100 or 200 feet below, that I was suspended above a desert, like an alien on a reconnaissance mission to earth after some disaster. Dive too early in the morning, and some of us are still dreaming, I suppose. Watery visions.

We take exotic fish and invertebrates for granted out here: leaf fish, stonefish, scorpionfish, mantis shrimp with their headlight eyes, Christmas tree worms. Disturb the current near them and they all shoot back into their holes like a colony of Day-Glo prairie dogs. I wanted to go out at night and snorkel the lagoons formed by the receding tide, since this is when the octos hunt in numbers, but the captain informs me (even though this is his favorite thing to do) that sharks enjoy the routine as well, and liability rules prevent clients from following along.

Zoox Story

I like to watch the giant clams in action, which, when quickly closing up their silken mantels, can squeeze out volumes of water almost instantly. The outer lip muscle of a giant clam is laced with aquamarine streaks. These are zooxanthellae (zoox to the marine biologists), which are embedded single-celled plants, living symbionts that photosynthesize and provide the clam with sugars. Corals are colored in the same way, and when a coral is bleached, it means these zoox are expelled, killing and blanching the animal and leaving only a pale skeleton. A rise in water temperature of only a degree or two beyond annual highs, due to natural El Ni-o events or heightened by greenhouse gases and global warming, can cause coral bleaching, which has stricken the GBR several times in the last 10 years, notably in 2002. "Projections for the future based on highly accurate models of global climate dramatically depict a scenario of wholesale mortality of the world's coral reefs," wrote leading Australian researchers in a recent study, and this could well be true.

Back at the Scripps Institution of Oceanography in La Jolla, Calif., I talk with Nancy Knowlton, one of the world's experts on bleaching events. "Things are getting worse," she says, "but there may be cause for hope. Not all symbiotic algae are the same, and some have been found to be resistant to warming temperatures." If these varieties become more prevalent, we may be in better shape than previously thought, though diversity will be restricted.

Thank Cod! as oceans activist David Helvarg likes to say. Not to worry. Too much. "Don't worry," Captain Pete tells me, "because worry brings ulcers, and you can't drink if you have an ulcer." Yet a sign hangs on the galley fridge: "Drinking and Diving Don't Mix." Five dives a day, and the only stimulant I crave is sleep. The voyage ends with, yes, a sing-along above the dive deck. AC/DC, the Church, Slim Dusty, Harry Chapin and the Eagles-Down Under favorites, or at least favorites of the captain, who wields a mean and sober guitar. Before dawn the last day, the captain drops my bags on Marlin Jetty in Cairns, and I cab to the airport. It's not full light until we fly over the open ocean, blue, smooth, deep, abyssal. I miss the shallows and the crevices of the reef already.

Dive In

Water Conditions: Expect water temps in the mid-80s in summer throughout the central and northern Great Barrier Reef, but surprisingly cool mid-70s in winter. Water clarity inside the Great Barrier Reef is affected by tides and surge, and averages 40 to 60 feet, with an occasional high of 100 feet. Outside the reef, visibility averages a reliable 50 to 100 feet and often soars to more than 200 feet out in the Coral Sea.

Climate: Seasons are reversed-December through February is summer; June through August is winter. In the tropical north of Queensland, daytime air temps vary from the 80s in winter to the 90s.

Getting There: Qantas offers service from New York (JFK), Los Angeles, San Francisco, Honolulu and seasonal service from Vancouver. www.qantas.com.

Entry Documents: A passport and visa are required.

Money Matters: The official currency is the Australian dollar (AU$$1 = US$1.32). Departure tax is usually included in airline ticket price.

Electricity: Throughout Australia, the voltage is 230/240 volts, 50 cycles. The power point sockets are three-pin flat, which can accommodate two-pin flat.

Tourism: www.australia.com and www.destinationqueensland.com.

Dive Operators: For detailed information on Australia's Great Barrier Reef, go to TripFinder on our web site at http://dive.scubadiving.com/tripfinder.