It's night-time, I'm in the open ocean with nothing but a torch and a snorkel, and there's a shark lurking metres away.
It moves stealthily, swaying back and forth the way a snake slithers, its eyes unblinking, its gills barely moving. I can hereby confirm: hair actually can stand on end underwater.
Fortunately, I spot a white tip. It's a reef shark - a largely non-threatening, smallish member of the sharp-toothed family. But it doesn't help quell my uneasy feeling about snorkelling by moonlight a good 12 hours away from the nearest land mass.
I'm in the Rowley Shoals, a trio of coral atolls about 300 kilometres west of Broome in Western Australia.
Sprouting from the ocean floor from depths of 440 metres, the pear-shaped atolls lie in a marine park on the edge of one of the widest continental shelves in the world.
It's the sort of place that has you glancing around, looking for David Attenborough. One of Earth's last untouched marine wildernesses, it's in essence a giant aquarium, home to 688 species of tropical fish and 233 coral varieties.
On a good day - in November, when trade winds cease and the water glasses off - you can see as far as 60 metres through the multi-hued ocean, spotting huge, fearless potato cod from the bow of the boat, schools of hump-headed maori wrasse or clusters of cobalt-blue staghorn coral. The clarity is magical.
The shark skulks off, and I spy a creature with tasselled fronds that unfurl to take in passing ocean minerals. I stretch out my hand but the slender arms shrink back in, revealing an animal that looks like seaweed. A tiny, floating crab lands on my hand and a muffled scream escapes through my snorkel.
As I shake it off, a pink shrimp scuttles over an urchin, whose red fingers probe mottled, coloured coral. Pearlescent fish hang suspended in the water until my light illuminates them and they dart back to the safety of the labyrinth below.
I click the underwater torch off and marvel at the dappled light dancing on the seabed, thrown by the half moon.
I've joined an eight-day cruise through the remote shoals on board a 26-metre luxury catamaran with only 13 others - all divers - and six crew.
The Broome-based Great Escape Charter Company visits this underwater wonderland each November, cruising to reef networks and coral gardens many divers claim rival the Great Barrier Reef.
The skipper, a strawberry-blond sea dog named Jez, has been navigating these current-fuelled waters for 24 years.
Even so, the wonder hasn't worn off: "It's something you look forward to for the whole year; it's like a reward," he says, putting aside his larrikin sense of humour for a moment. "The corals, the fish, the pristine environment: it's untouched. I don't have words to describe how awesome it is, because it's just so good."
It's a delightful 28 degrees in the water, rendering wetsuits unnecessary - though by the end of the week we water babies have acclimatised, petulantly shivering as we clamber back on board.
We've become fussy about nature's slide show, too, complaining if we don't spot a ribboning moray eel, marine turtle or chameleon cuttlefish on each of our four-times-daily adventures.
One thing that never gets old is the five-star food, served up by an exceptionally talented 24-year-old chef named Mitch - sometimes even while we're relaxing in the on-deck spa.
He carves freshly caught tuna into sashimi, wraps basil leaves around wonton prawns and dips seasoned quail thighs into wasabi, more than refuelling our energy reserves for the next plunge.
As the sole snorkeller, I swim alone above the divers, watching as their oxygen bubbles mutate like mercury jellyfish. At times, the significant tides sweep me away from them, over shallow corals that fan over the seabed, hosting fish as thick and bright as confetti.
The tides rise and fall by about four metres each day, turning boat navigation into a fine art.
Jez's buoyant ride is the only commercial cruiser that can float right up to the treacherous reefs, necessitating a high degree of concentration as the water pulls the vessel in its direction, whatever direction it's travelling.
"I shit my pants the first time I did it - not quite, but you know," he grins. "You have to do it quick, you've got to pre-empt turns and know where you are the whole time."
The tides deliver something else much more fun: drift snorkelling. Deposited at one end of a coral channel, we zoom past giant clams pouting Botoxed lips, and bulbous anemones harbouring clownfish families as the current pulls us along.
We gradually pick up speed, seemingly flying through the water as the activity along the coral walls passes us by. It's the closest I'll ever get to being Astro Boy.
At sunset, we board dinghies and head to a white sandy disc that's been flirting with us for days.
A semi-circle of chairs is set up facing the setting orb, Eskies are lugged up the beach and freshly made pizza is delivered from the boat. We comb the Bedwell Island coast, feeling aerated sand beneath our feet and spotting plover birds sheltering behind weathered driftwood.
Sea snails collectively dash towards the retreating water as the earth quietens.
You'd think the peachy hues of the sun's retreat would've topped the week off nicely, but a pod of spinner dolphins puts paid to that.
As the catamaran ploughs through the sea, destination Broome, a dozen of the small tri-coloured cetaceans spot us, tearing across the ocean until they reach the bow.
I don't know if they can hear our childlike squeals, but they jump and plunge like hyperactive acrobats until we hit the edge of the marine park, when they disappear back into the watery wilderness they're so lucky to belong to.
Fleur Bainger travelled courtesy of The Great Escape Charter Company and Australia's North West.
Who knew? Whitehaven Beach in the Whitsundays has this year been ranked third-best on TripAdvisor's list of the World's 50 Best Beaches.
Where The Great Escape Charter Company. Suite 4, 15-17 Dampier Terrace, Broome. (08) 9193 5983, greatescape.net.au.
Getting thereQantas flies non-stop from Sydney to Broome on Tuesdays and Saturdays for about $586 one way, including tax (5hr 10min).
Cruising there Five- and seven-day trips depart each November from Broome, WA, suited to both snorkellers and divers. The Great Escape Charter Company is a fully accredited member of PADI scuba-diving society.
Executive staterooms have queen-size beds (or twin singles), en suite, flat-screen television with DVD player and airconditioning; wi-fi internet access can be purchased on board and works 12 hours from the mainland. This year's prices range from $4959 a person, twin share, in a horizon view stateroom for a five-day trip to $8145 for seven nights in a panoramic view stateroom.
A small number of other cruise operators visit the Rowley Shoals in October and November, including True North, K2O and Kimberley Expeditions. The Great Escape, a catamaran, is the only boat that can enter the coral gardens, while the others moor outside the reefs and enter via dinghies.
More information australiasnorthwest.com.au.
- Sydney Morning Herald