Holding my breath, I can hardly believe what I’m seeing: the gaping mouth of a giant shark is heading towards me, with only a few metres of ocean between us.
I demonstrate my best impression of Michael Phelps, wishing I had even a fraction of the legendary American swimmer’s pace.
Despite thrashing my arms and legs frantically, I’m not in a state of panic or fearing for my life. Instead, I’m trying to keep up with a six-foot whale shark that appears to be more interested in plankton than my pale pink Derbyshire flesh.
The biggest fish in the world is gliding along in front of me, propelled by a huge tail moving from side to side. Easily recognisable by its distinctive white spots, the timid mammal then disappears deep into the ocean.
I’d wondered what I might be letting myself in for when I signed up for a trip to see whale sharks in Western Australia’s impressive Ningaloo Reef, but Jenny, a young marine biologist from Ocean Eco Adventures, had assured me I was in for a treat.
She was certainly right.
The World-Heritage listed Ningaloo Marine Park boasts more than 250 species of coral and 500-plus types of fish. Given its proximity to the shore, it’s also easily accessible.
Whale sharks can be found in the reef from April to July, with the help of a spotter plane, allowing tourists the opportunity to swim with these gentle giants of the ocean.
Back on the boat, I catch my breath, but it’s not long before our plane picks out another whale shark.
As we dive into the water, the curious creature circles us. It might sound like a nightmare scenario but it actually enables us to get a better look at one of the most rare fish on the planet.
And the novelty has certainly not worn off by the time I clap eyes on a third shark.
Soaking up the sun after lunch before heading out for one last snorkel, I’m beckoned onto the top deck amid a frenzy of excitement.
At least 100 spinner dolphins are putting on a show of their own, leaping in and out of the ocean. Bright blue damselfish, green and purple parrotfish and dazzling orange clownfish illuminate the water just below me.
Fortunately, you don’t have to spend all of your time below the surface to appreciate what Ningaloo Reef has to offer.
Stretching 260 kilometres along the length of the North West Cape, the coastline can easily be explored on a kayak.
Heading out from the quiet town of Exmouth along a dusty road to Osprey Bay, I prepare to swap the luxury of the Novotel Ningaloo Resort for a night camping on the beach, as part of a two-day kayaking excursion.
Two friendly couples from Sydney join me, and it immediately becomes apparent that they are just as competitive as me, as they joke about who might be out in front.
“Stick close to the shore, or you might end up in Timbuktu,” says our guide Neri, as the golden sandy beach fades a little too quickly into the distance, thanks to my poor ability to steer in the right direction.
My new Australian friends may be old enough to be my parents, but they are soon disappearing ahead as I struggle to inch forward.
In reality, there’s no reason to rush; gliding slowly, I watch ospreys and eagles soar into the sky, while cowtail stingrays and turtles swim below as the scorching sun reflects off the clear blue ocean.
We stop for a snorkel just off the shore and I swim alongside grass emperors and spangled emperors, along with scores of different exotic-looking fish.
When we arrive at South Mandu, my arms are throbbing. I wrestle with my tent before finally managing to put it up - with some assistance - in time to watch a spectacular sunset on the beach.
As Neri whips up a tasty stir-fry, we sit around the fire drinking whisky - which flows just as easily as the conversation.
As darkness falls, we stroll along the starlit beach, watching stout longtom fish spring into life as they leap from the water.
Despite being exhausted, I only have a few hours sleep as I contemplate what the noises outside my tent might be.
Staggering outside in a daze the following morning, I can still hear a hissing sound, which I’m convinced is a snake. Fortunately though, it’s just a kettle boiling on the beach.
Following a strong early-morning coffee, I’m back in the water hastily paddling against the tide. But my efforts are rewarded when we reach the peaceful Turquoise Bay, one of the most beautiful beaches I’ve ever set eyes on.
As I drag my kayak onto the beach for the final time, my forearms feel like Popeye’s - probably the result of a week spent swimming with whale sharks and paddling solidly for two days.
It’s been worth it though, I tell myself. Along with vivid memories of an outstandingly beautiful part of the world, I also have some bulging biceps to return home with. Big enough, in fact, to challenge a giant... albeit a very gentle one.