The plane shudders to a halt on Learmonth airport's truncated runway, 740 miles north of Perth in Western Australia. Our group piles into a 12-seater van for the 80-minute drive to Coral Bay, from where we'll set out to follow the Warlu Way. According to Aboriginal myth, Coral Bay is where a giant warlu, or sea serpent, once emerged from the ocean and slithered inland, carving out gorges, ravines and waterholes as it went.
A self-drive route of nearly 1,500 miles today follows the trail of the warlu through some of Western Australia's most beautiful and remote regions – the Gascoyne, Pilbara and Kimberley. There are eight of us, so we've organised a van and a driver for the section we'll be covering – 390 miles from Coral Bay to Karijini National Park, where the warlu's fabled route inland is most evident today.
We start our adventure by exploring Ningaloo Reef, home of warlus both large and small. From Coral Bay, we transfer by dinghy to Shore Thing, the catamaran that will be our home for the next two days. Skipper Luke Riley and his wife Lannie run live-aboard sailing trips along Ningaloo. I'm buddied up with Steve, who's visiting from the UK, and dive-master Dee for our first dive at "Asho's Gap", where we find ourselves engulfed by hundreds of two-foot silver bludger trevally fish. The slate-grey cabbage corals below are home to schools of tiny damselfish, pairs of spangled emperors and harlequin sweetlips.
Over dinner talk turns to the reef species we're hoping to see. I confess I've never swum with a manta ray and Luke smiles when I ask what our chances are. "Now and then I help a research team gathering data on local manta ray populations. On one day I was able to confirm swimming beneath 35 different mantas," he says.
The next day, little more than an hour after breakfast, we're slipping in off the transom for a quick snorkel over a pale green garden of stag-horn coral and we see our very first warlu – an olive sea-snake. Luke tells me that a typical day on Shore Thing aims to satisfy snorkellers and divers alike. "Even for divers, it's fun to get in for a snorkel and see the reef in a different way. With the currents we get, it's like riding a see-through conveyor belt over the top of an aquarium."
On our next two dives we see species found only at Ningaloo: several jet-black sailfin catfish and a white-eyed moray eel, its entire three-foot length, a translucent white. But nothing could have prepared me for our last dive, on a site Dee calls "the Lost City", after its rubble of coral walls, caves and crevices. At around 50ft down, we find a leopard shark being attended by cleaner wrasse. As if driven by some sixth sense, Steve and I spin around to the deep blue yonder: barely 30ft away, a 10ft tiger shark ghosts by like an assassin, its unmistakable tiger-stripe markings eliciting a shared moment of wide-eyed awe.
Then it's all aboard the van again and we're on our way 90 miles north to Exmouth on the warlu road. Outside, the landscape is an expanse of burnt-orange desert, spinifex and termite mounds. The Ningaloo creatures that commonly figure in local Aboriginal stories are the warlu, manta ray, whale shark and turtle (all depicted in ancient rock paintings around Western Australia) and we have a fair chance of finding all four on our whale shark tour with Ocean Eco Adventures.
When the skipper spots a shark, the first group of 10 slides into the water and fins alongside for five minutes, before the boat swings around to pick them up and drop the rest of us in. Over the next two hours, we each manage to swim alongside six different sharks. Just as I start stripping off my wetsuit, the skipper suggests we look out for manta rays. Sure enough, within 20 minutes the entire group hops in to snorkel with four manta rays just a few feet below.
On the run home I ask Steve about his first trip to Ningaloo. He needs little encouragement: "There isn't a dive destination I know of where you could expect to see all the different species we've seen, especially in just three days – humpback whales, dugongs, manta rays, whale sharks, leopard sharks, tiger sharks, nudibranchs. Seeing even one of those species would make for a perfectly acceptable dive almost anywhere else." Steve should know: he's been editor of Diver, a UK magazine for scuba enthusiasts, since 1996.
Our group are eager for an early start on the 350-mile haul inland to Karijini National Park. We break for morning tea at Bullara Station with owners Tim and Edwina Shallcross and I feel a twinge of regret that we don't have the chance to stay for a night. The former sheep station's rustic rooms and the prospect of a crackling outdoor fire, shared with fellow travellers, are enticing.
We near the foothills of the Hamersley Range and all around is the rust-red iron-rich earth that tells the tale of Western Australia's decade-long mining boom. The gorges of Karijini are perhaps the best-known feature of the warlu's travels, winding their way through a glorious desert savannah, strewn with mulga trees and ghost gums.
Karijini Eco Retreat is made up of several camping grounds, a basic reception and dining facility, and 50 permanent tents. When the sun comes up, we walk into Hancock Gorge to photograph Kermit's Pool and examine its layered banded ironstone which, at 2.5 billion years old, is the world's oldest exposed rock. Nevertheless, we can see bolts fixed to the gorge walls that are used for canyoneering day trips, providing access to otherwise inaccessible pools and waterfalls. Joffre Gorge is just a steep scramble in and out, so we make use of a sun-drenched freshwater pool for a swim. From a lookout above Weano Gorge we watch hikers wade from pool to pool, far enough away that most of what we can make out is the ripples left in their wake.
According to legend, the warlu settled in a spring in the heart of the Pilbara region, and there he stays to this day. From Karijini, it's another half-day's drive northwest along the Warlu Way to Millstream-Chichester National Park – where, in a desert pool, the warlu finally found his home.
Travelbag (0871 703 4240; travelbag.co.uk) six-night Warlu Way package from £1,349pp including two nights in Perth, two nights at the Novotel Ningaloo and two nights at Karijini Eco Retreat, seven days' car hire from Perth and Qatar flights from Heathrow to Perth via Doha.
Sail Ningaloo (00 61 402 110 427; sailningaloo.com.au) from April-December, from A$1,700 (£1,062) per person.
Ocean Eco Adventures (00 61 427 425 925; oceanecoadventures.com.au) whale shark tours, April-July for A$395 (£247) per person.
Novotel Ningaloo Resort in Exmouth (novotelningaloo.com.au) doubles from A$320 (£200),.
Bullara Station (bullara-station.com.au), has doubles from A$140 (£88).
Karijini Eco Retreat (karijiniecoretreat.com.au) has safari-style tents from A$315 (£197)