Shifting sands: This gorgeous island in Queensland is on the move

K'gari is gradually getting further from the mainland," says our guide, Guy. "Erosion is affecting the western side of the island but sand from as far away as the Murray Basin and the Hawkesbury River, and from rivers in northern NSW, is being deposited on the eastern side, so the island isn't actually getting any smaller."

We're on the Beauty Spots Tour of K'gari, just off the coast of south-east Queensland near Hervey Bay, and Guy is going full geologist as he manoeuvres the 4WD bus over the colossal ruts in the road caused by recent rain. Members of the English family who've chosen to sit in the back seat are squealing and laughing as they're bucked by every bump on the trail.

We're almost at Boorangoora (Lake McKenzie), the island's famed perched lake. K'gari has a huge underground aquifer, but this body of H2O is pure rainwater. It doesn't even run off into the sea. Although all these facts are interesting, the real reason people flock to Boorangoora is because it resembles paradise. Soft white sand leads to turquoise water turning deep blue where the depth increases suddenly. The only critters who live here are a few turtles that have adapted to life in the slightly acidic water.

It's early when we arrive and, since it's winter, there is no one else around. But a Queensland winter is mild, warm and perfect for swimming. When it's time to set off, no one wants to leave.

If that was the end of the tour, you'd be satisfied, but it's early in the day and there's much more to see. We venture into forests, where you have to squint to glimpse the top of the sun-pierced canopy, and follow creeks fed by springs where the water is so clear it is almost invisible. On the eastern side of the island, only accessible by 4WD, whales can be seen breaching beyond the waves and coloured sands form incredible rock-like formations. A wongari (dingo) has found some fish guts an angler has left behind and is scarfing them down on the sand. We stop for photos at the wreck of the SS Maheno. The ocean liner was being towed to Japan for scrap metal when the rope snapped during a cyclone and it was washed onto K'gari's sand. It's now rusting away, that same sand slowly engulfing its bulk.

The day-long tour takes in just a small portion of K'gari, which, at 123 kilometres long, is the world's largest sand island. The home of the Butchulla people, it became known as Great Sandy Island after colonisation and, in 1842, the name changed again to Fraser Island, after Captain James Fraser and his wife Eliza, who'd been shipwrecked there a decade earlier.

Initially, exploited for timber and sand (all that has stopped now), K'gari was World Heritage listed in 1992. There are several reasons why, but one seems almost impossible. Over thousands of years, vegetation has decomposed, leaving behind soil that is up to 30 metres deep (on Earth, the average depth of soil is one metre). Now, the island is the only place in the world where you can find subtropical rainforests growing entirely on sand. In June this year, in a small ceremony attended by Butchulla elders near Wanggoolba Creek, the island's name reverted to the traditional K'gari (pronounced Gurri).

Most visitors spending more than a day on K'gari stay on the western side of the island at the luxurious Kingfisher Bay Resort. It forms its own ecosystem. There's a sunset bar down by the jetty. The pub boasts a pool. There are boats for sunset cruises and tours along the west coast to explore the other smaller islands of the Great Sandy Strait. Surprisingly, K'gari is the only one made of sand - nearby Picnic Island is volcanic rock and shells. You pass them all when you sail to Platypus Bay, where the whales come to play. On a sunny day, we spy humpbacks and their calves, some languishing in the warm water, others flexing their tails or coming close to the boat to satisfy their cetacean curiosity.

Kingfisher Bay also has a small army of rangers. I first meet ranger Letty during a Bush Tucker Talk and Taste with chef Shubhankar. On a platter in front of us is a selection of salts, spices, fruits, pastes and pestos, all made using native ingredients. Some, like the lip-smackingly tart lemon aspen and numbing cinnamon myrtle, grow on K'gari. Others, like the bopple nut (macadamia), were revered, used during ceremonies or its oil extracted to preserve paintings.

The following evening, Letty and Jackie lead a night-time nature tour. We start at a stream that runs beneath the boardwalk and meet Barbara, the short-finned eel, who snaps at a tiny gudgeon that crosses her path. We move on to see trapdoor spiders and bats feasting on the nectar of flowering satinays. The prize, though, is seeing a tiny sugar glider in flight. We're on the driveway when Letty spots one. Then it takes off, sailing about 30 metres to another tree.

"That's one of the longest glides I've ever seen," she exclaims. Then another sugar glider swoops between branches. There's a turf war going on, Letty explains, with each male unhappy about the other's presence. For the next 15 minutes, it's like watching acrobats perform beneath the canvas of a big top. We gasp and stare, eyes wide and torch beams following the action. Then they stop, either spent or satisfied the other means no harm, and we're left to retreat to our rooms. When I say good night to Letty and Jackie at the resort foyer, it's not a mere pleasantry. In fact, this has been a great night.

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Getting there: The SeaLink ferry to K'gari leaves from River Heads, about 27 kilometres south of Hervey Bay, four times a day. The crossing takes 50 minutes. Kingfisher Bay Resort can organise transfers from Hervey Bay Airport or your accommodation. See sealink.com.au

Staying there: Kingfisher Bay Resort has resort hotel rooms, villas and holiday homes, along with several restaurants and bars, a day spa and tours. Standard resort rooms start at $199 a night. See kingfisherbay.com

More information: visitfrasercoast.com

The writer was a guest of Kingfisher Bay Resort.