"OOH, AH," SAYS THE WOMAN next to me, looking up from her glossy brochure. 'There it is.' Lizard Island looms into view below the right wing of our twin-engined Bandeirante. It seems too perfect to be real - as though an air brushed image had floated down from the brochure on to the blue canvas of the sea. First comes the proud outline of the island, nudging its single, craggy peak into the cloudless tropical sky. Flying in lower we see a tiny shoal of yachts nibbling at the curve of a white beach; the surrounding water like a giant pool of wet blue paint. Suddenly, there is a flash of rooftop and the resort, half hidden among a grove of coconut palms, races by under our feet. Time for another quick 'ooh, ah' before we touch down on the single runway and begin taxiing towards the modest terminal building. An air-conditioned mini-bus is waiting to take us to the resort - a five minute journey through the khaki-coloured Australian bush. After the tourist crush of Cairns, Lizard Island seems self-indulgently peaceful. But the pervasive sense of calmness is carefully orchestrated. New arrivals are swiftly surrounded by managers, under managers and waiters. The smooth mechanism of hospitality moves into gear. A tanned waitress in a floral shirt and smart white slacks appears at my elbow: 'Excuse me sir, would you like a glass of cold water before checking in?' We are served tea and designer sandwiches on the terrace while our bags travel noiselessly by electric buggy to our rooms. I am beginning to understand the Lizard catchphrase, 'One of One'. To maintain this sense of exclusivity, the resort, 150 miles north of Cairns, employs 80 permanent staff; one member of staff for each guest on the island. Since buying the property from Qantas, P&O has spent £5.3 million improving and refurbishing Lizard Island. The result is a luxuriously eclectic mix of influences; classic Australian beach architecture, with a dash of the South Seas and a dollop of British Raj chic (wicker chairs, fine linen and overhead fans). Today's crisp-looking international establishment is a far cry from the fishing camp which first occupied the site. Even the coconut trees were imported to create a tropical island feel.

Back in the 1970s Lizard Island was a magnet for roughneck fishermen hunting black marlin - among them the American actor Lee Marvin, who made an annual pilgrimage here. Little remains of this colourful chapter in the island's history, although the resort still sponsors a marlin competition every October. The emphasis has shifted from big-game machismo to marine appreciation. From dawn to dusk pale-skinned Americans, immaculately dressed Italians and well-upholstered Aussies can be seen setting out to explore the Great Barrier Reef. Whether taking part in an organised dive or mounting their own expedition by motorised dinghy (picnic hampers are available on request), no part of the reef escapes their scrutiny. Curiously, the powdery white beaches are left largely undisturbed. Such is the lure of the coral and its exotic inhabitants that hardly anyone goes to the beach on Lizard Island. Having spent much of the previous month on decrepit outrigger canoes in the Pacific, I was keen to spend the first day exploring the island by foot. Like the beaches, the island's park-like interior (which includes rolling grassland, dense eucalyptus forest and mangrove swamp) is mostly deserted. I passed three people, all visiting yachties, the day I went for a hike. At 1,200ft, Cook's Look is the highest point on the island. I had the panoramic view to myself. It was from here that Captain James Cook charted a safe passage through treacherous reefs and out to open sea. A stone cairn marks the spot where the intrepid Yorkshireman stood on August 12, 1770. It is not difficult to imagine the awe he felt when gazing at God's work. He called the Great Barrier Reef 'the insane labyrinth'. For him it was a sharp-edged coral prison. Having already narrowly escaped wrecking his ship, Cook was not ready to risk a second disaster.

When he came here, it was by necessity; he stayed long enough only to find an escape route through the reef, replenish his stocks of fresh water and become acquainted with the island's population of monitor lizards. 'The only land animals we saw were lizards and these seem to be pretty plenty,' he wrote in his diary. Two centuries later the bowed-legged monitors are still a familiar sight. Despite their size and ugliness, the lizards are faintly comical. Perhaps it's the John Wayne walk - but be warned, they can bite. Then there are the geckos, skinks (small striped lizards) and a species known as legless lizards. We've all met some of these on holiday. For an island of its size, Lizard has a surprising variety of birdlife. Unlike much of the Pacific, where birds tend to end up in the pot, you'll find 50 different species on Lizard, including the yellow-billed sunbird, the pheasant coucal, the sooty oystercatcher and the osprey. Bird Islet is a tern sanctuary. Away from the resort there is little evidence of previous human occupation, apart from a ruined stone cottage at Watson's Beach. It was here that Mary Watson, the wife of a Scottish sea captain, was attacked by Aboriginal islanders, the Dingaal, in 1881. With her husband away on a fishing trip, Mrs Watson - with her baby and Chinese servant - fled to sea in an iron boiler. All three drowned. This event seems to have ended the Dingaal's 10,000 - year occupation of Lizard Island, or Jiigurru. More recently their descendants have begun revisiting the island, and now advise the Queensland Parks and Wildlife Service on its conservation and management.

Today, Lizard's only full-time residents (apart from the resort staff) are a handful of marine biologists on the other side of the island. Run by the Australian Museum in Sydney, the research station attracts scientists from around the world. Even for a committed land-lubber, a tour of the research station was enough to produce a hankering for underwater exploration. I was intrigued by the reef's stranger inhabitants, such as gobys, tiny fish that can change sex at will. Sea cucumbers (or beche-de-mer) also became something of an obsession (the leopard sea-cucumber extrudes toxic poo). With 125 known varieties of sea cucumbers, it's time the producers of X-Men turned their attention to the ocean floor. The next morning I joined a snorkelling group to the inner reef. Like everything else on Lizard island, the trip was superbly organised and the reef itself magical and unspoilt. But an impromptu appearance by three humpback whales caught everyone on the hop. Battering into a heavy swell, our boat almost ran into them - their tails majestically waving in the air. 'Let me assure you this does not happen every day,' said the captain. 'Most of us who work here never get to see anything like this.' When the three 40ft whales began breaching, everyone wore the same gormless grin. A stunning display of synchronised swimming by the world's largest mammals but just another 'ooh, ah' moment on Lizard Island. The three blubbery extroverts finally went on their way and we returned to our own aquatic mission. After all, I had an appointment to keep with a toxic sea cucumber.