A hundred kilometres off the coast of Gladstone, on the outer edge of the Great Barrier Reef, is a tiny island made from the bones of coral. The four-hectare white-limestone mound is the remains of thousands of generations of polyps, minuscule marine creatures forming reef colonies. It is animal and mineral, there is no soil in sight, and the twisted plants there have dug deep to find dirt in which to take root. In the middle of the nineteenth century these plants caught the eye of a naval surveyor who, mistaking them for a solitary figure of green, gave the cay its name: One Tree Island. Now the island is a research station, a clump of nine shacks where scientists study the reef and where its director, Maria Byrne, works to secure the station's future.

It is May when Byrne convinces a property developer to meet her at Brisbane Airport. She hopes he'll visit the island and be persuaded to sponsor students' travel costs, and she wants me to come along and write about the station. An energetic marine biologist and the daughter of an Irish factory worker - "I pulled pints for farmers when I was 11" - Byrne is friendly and forthright, and speaks in flustered bursts. "I'd be happy with a legacy of six scholarships and a functioning station," she tells me. The developer, Craig Dowling, is late.

Sydney University has held the lease on One Tree for 33 years, but with less than 20% of the university's operational funding coming from the federal government, Byrne, like many academics, feels pressure to develop industry partnerships. She turns to a full-page ad in the latest New Scientist: Win 5 days on the Great Barrier Reef. Participate in research and stay overnight with the scientists on One Tree Island. "I had to change the wording. It initially read ‘Spend a night with the scientists'," she says.

Byrne's loud mauve-and-pink shirt whips between travellers as she juggles a Filofax and a mobile phone while dragging heavy luggage off a carousel. "It's the carrots and broccoli," she tells me. There are 15 students staying at One Tree this week. Byrne worries about their food - "they need their vitamin E" - as she performs mental astronomy for the trip. She was forced to organise our visit around a new-moon cycle, when the sun and moon exert a strong magnetic pull on the earth, causing the oceans to flatten out more than usual. "We're restricted by the tide, the time and the weather. We can only land the helicopter at very low tide, twice a month, during the new moon and full moon."

We're also restricted by Craig Dowling's schedule. He arrives at the airport, big-chested and dressed for The Land. At just 38 he is the director of Buildev Development Queensland, a $380-million property-development arm of the Buildev Group, and time, for him, really is money. Which is why we're travelling to Gladstone in his company's private jet - "it saves us 30 minutes," says Byrne - and why we'll get to One Tree by helicopter instead of by boat. "What stress will this excursion put on the itinerary?" Dowling asks his PA over the phone. Tomorrow he's due to meet Nicole Kidman.

The three of us wait in a cramped hut for the jet to arrive and, from nowhere, Julie Bishop walks in. This is Byrne's moment, her chance to pitch the importance of the research station to the one person who could really help. But the education minister, in a cream suit and pearls, is preoccupied and has little time. She shakes Byrne's hand and escapes into the women's bathroom.

Inside Dowling's seven-seater jet we settle into beige leather seats. "My wife and I remember when we had $50 in our wallet and we couldn't pay the mortgage. Things are different now, but I'm still just one of the worker bees," he says. Behind the sunglasses, his eyes look permanently moist. Five years ago, before he took the big job with the big pay, he slipped on tiles at home, cracked his back and was left paralysed from the waist down. After five weeks in hospital and 18 months in rehabilitation, he could walk again, although he has no feeling down one side of his left leg. "Humans don't realise how fragile we are," he tells me.

High above Maroochydore, Dowling points out ‘Old Woman Island' and tells us its tale: how two Aboriginal lovers were forbidden to be together; how an elder created the Maroochydore River to divide the land and keep them apart; and how the island is the teardrop of the woman. "When I built Surfair I found out about the story. It's on a plaque in the resort," he says.

In the Gladstone Airport lounge sit tables with parents, kids and plates of tired-looking chips. Behind them is a wide sign: A young vibrant region, full of character. Buildev is co-managing a 128-hectare development in Gladstone, and Dowling is confident that a relationship with One Tree will reflect favourably on his project. The company already sponsors student prizes, "which is good PR for us and good PR for the island," he tells me.

We travel east. From the thick windows of the helicopter, the surface of the ocean around us is an infinite skin. In the distance One Tree's five-kilometre reef looks like a discoloured graze on a perfect blue body, and the islet at one end is a lonely, ridiculous patch of green. "A tropical island. I've got to get one of these," says Dowling. He may not be joking.

It was 10 January 1843 when J Beete Jukes, a geologist aboard the HMS Fly sent to survey the Barrier Reef, first saw One Tree Island and named it. The next day he set foot on the rubble cay. Despite the "low succulent plants", the "multitudes of young terns" and "the shoal lagoon", the island and its reef "looked simply like a half-drowned mass of dirty brown sandstone, on which a few stunted corals had taken root". The one tree, he wrote, was in fact a small clump of "the common pandanus".

What he didn't write about was how small he must have felt on this low-lying mound, close to the edge of the continental shelf, where the land is not land but a coral floor too high for the sea. Here, you are not so much on something as in it. The feeling is of awesome calm, a benevolent inversion of Yann Martel's island in Life of Pi, whose buoyant ball of algae wrapped itself around bodies and digested them, "their very bones leached of nutrients until they vanished".

Within minutes of arriving at One Tree, we pull on the unofficial uniform - a full-length wetsuit - and join the other black, seal-like creatures moving in and out of the water without effort. It is as if ‘land' and ‘sea' are peculiarly artificial distinctions to make about a world made of the same stuff. Byrne takes us snorkelling, our bodies held gently in each reef pocket, tumbling in the tug of the tide. Silently, a giant turtle flaps its wings in brilliant weightlessness.

Because One Tree is a Scientific Research Zone and part of the Great Barrier Reef Marine Park, visitors, including the two caretakers who live here six months a year, observe strict regulations. The station relies on rainwater; solar panels provide 99% of the energy. Researchers don't collect species without permits - fishing is not allowed - and during the bird-nesting season there is little room for humans to move about.

Craig Dowling hasn't said much since we landed. "Wooing investors is time-consuming," a researcher whispers to me, but it's something else that's keeping Dowling quiet: the island disrupts familiar ways of being. One Tree is not about the possibility of development and expansion, but about reforming the relationship between person and place. We're not just getting back to nature; we're enveloped in it. Breathing the wind, swaying with the currents, we do more than feel the ocean; we merge with it, the partition between our bodies and place becoming porous.

At night, after our one-bucket-per-person baths, we're shown to small rooms with timber bunks. Tomorrow, Maria Byrne will rise before dawn, prepare coffee and hand us T-shirts with One Tree Island logos. Tomorrow, Craig Dowling will retrieve 77 phone messages, meet men in suits at Gladstone and jet off to see Our Nic. For now, though, we sleep, with the louvres to the rooms ajar, the salt working its way through our clothes and bones, and the coral skeletons resting below us.