'Is this the real life?" I warble through clenched teeth into my rubber mouthpiece. "Is this just fantasy?" There's no accounting for what tunes enter your head when you're being dragged backwards through the Arctic Ocean under instruction to sing "as loud and high as you can".
Happily, this is no water torture. I am here willingly as a guest of Seal River Heritage Lodge on Canada's Hudson Bay. The idea is to get closer to belugas, the small white whales that gather here in their thousands every summer. I have already seen them from the air: scattered like rice over the wrinkled tablecloth of the bay, you could hardly miss them. But now, face down in the dark, choppy waters, meeting one is a more daunting prospect.
A dry suit keeps me both warm and buoyant. Andy MacPherson, our guide, is some 20m behind me in the Zodiac, paying out the line in which my feet are looped as the boat inches forward. I should know what to expect – we've had a thorough briefing; even watched a DVD – but I can feel my confidence ebbing away, along with my warbling, into the murk.
Then I hear it: an electrical hissing and buzzing, interspersed with bright, R2-D2-style clicks and whistles. Not for nothing are belugas known as sea canaries. I redouble my own efforts – by now I've moved on to "The Girl from Ipanema" – and, on cue, a pale shape emerges at the sepia edge of my vision.
As I'm trying to make sense of this apparition, another whale arrives – much closer. Smooth, muscular and Dulux white, it passes on its back just two metres below me and stares up with naked curiosity. I can see its bulging forehead and endearing dolphin smile. Then another looms up from nowhere and scrutinises me, eyeball to eyeball, a foot in front of my face.
For the next 15 minutes I hang there, hardly breathing, as the belugas encircle me – almost, but not quite, making contact. When they disappear I need only start singing again ("Dancing Queen", "Wuthering Heights" – female vocals seem to do the trick) and they're back, sometimes in pods of four or five, grey calves piggy-backing on females. Their chatter pulses in and out of the murk like the tuning of a long-wave radio. "Who's the clown on the rope? Doesn't he know any Lady Gaga?"
Spectacular as the belugas are, it is another large, white Arctic mammal for which this area is best known. The ramshackle outpost of Churchill, from where we flew in two days ago, was once a booming port for the fur trade. Today its greatest claim to fame is the autumn gathering of polar bears, which sniff around the outskirts as they wait for the bay to freeze over, sometimes moseying downtown to see what's cooking.
Churchill is, apparently, bear-free during my brief stopover, though I heed the warnings and restrict my wanderings to Main Street. Seal River Lodge is a different story. The flight north takes some 25 minutes, and before we have even landed I spy two things below: first, a cluster of wooden buildings that must be the lodge; second, something large and white ambling past them, which can only be one of the neighbours.
Tundra swans flap heavily away as our Turbo Beaver floatplane touches down and taxis to the landing jetty. Andy and fellow guide Terry Elliot ask us to stay on the boardwalk as we wait for the luggage: "Don't want you guys meeting any bears just yet."
The message is repeated as hosts Mike and Jeanne Reimer welcome us into the lodge. "That front door you just came through?" says Mike. "Well, it's no longer a door. You never go out of it – unless you're with one of us."
Nobody protests; this summer's attack on a group of young British explorers in Svalbard, in which one man was killed by a polar bear, made headlines on both sides of the Atlantic. As we slap on insect repellent and don boots for our first hike, our guides run through the bear safety drill. Terry reassures the more anxious among us by revealing his arsenal of firecrackers, pepper spray and shotgun. He stresses, though, that this gear is to be used only as a last resort, and that a lusty yell and well-aimed stone will usually do the trick.
Soon we are tramping out along the shoreline below the lodge. The retreating tide has exposed a moonscape of glacial boulders across the mudflats, and it is behind one of these that we meet our first bear – having a kip. The long neck swings up, roman nose testing the breeze, before the head settles on massive forepaws, black eyes fixed on our approach.
With a relaxed individual like this one, Andy explains, we can get within 50 metres. So that is exactly what we do – single file at first, so as not to "intimidate" him; then, having reached a strategic shingle ridge, spreading out slowly to allow everyone a decent view. "Hey, big guy," says Terry, in low, reassuring tones. "Stay cool. We're just taking a look." On the face of it, you couldn't meet a more harmless-looking creature. The great, furry mound is outlandishly white against the tundra backdrop, and rolls over as though for a cuddle. But nobody's going any closer. It's a thrilling moment: wall-to-wall wilderness, with just us and – a few paces away – the world's largest terrestrial predator.
After a while, the bear gets up, shakes himself like an over-sized Labrador and saunters up the beach. Fur and muscle shift and bunch with fluid ease as he melts into the bushes behind. "Super-awesome!" murmurs Andy, reverently, even though he's seen it countless times.
Over the next few days we become more accustomed to the bears and venture a little further into their world. It's a wild place, certainly: from the sweep of Hudson Bay in front to the treeline along the southern horizon, we see no sign of humanity except the lodge itself. But it's far from barren: fireweed and marsh ragwort splash their colours across the shoreline; dwarf willows peep from the stream edges; and crowberries and cloudberries carpet the tundra's springy mattress. In fact, with the sun on our backs and the hum of insects in our ears, it's hard to believe the ground is solid ice just one metre below our feet. We reach into a fissure and feel it for ourselves. This may be a few degrees south of the Arctic Circle but we sit squarely on the permafrost.
Birds are everywhere. Sandpipers, godwits and yellowlegs keep up a shrill piping as they commute between tidal pools, while sandhill cranes and Canada geese cross the tundra in bugling skeins. Twice, a gyr falcon (think souped-up peregrine) sweeps like a fighter jet through the panicked ranks of ducks and shorebirds, but each time departs empty-taloned.
Even when out of sight, however, bears are seldom out of mind. While we crouch to photograph mountain avens or train binoculars on a red-throated loon, Terry and Andy keep up their methodical scanning of distant ridges and nearby bushes. And, should we forget, the huge, five-clawed tracks printed across every beach provide an eloquent reminder, and the chattering of Arctic ground squirrels – popping upright like prairie dogs – a handy alarm call.
Truth be told, there is no better viewing of bears than from the lodge. Inside the fenced compound is a wooden observation tower, from where we can watch them roam the landscape at our leisure. Mealtimes, meanwhile, are frequently interrupted by one swinging right past the windows; our waiters shrug resignedly as we kick back chairs and scramble for cameras.
On such occasions, it is us who feel like the captive exhibits. But the lodge makes a delightful zoo. Inside, safe from inquisitive bears, wild weather and ravenous mosquitoes, we enjoy fabulous food – caribou wellington, blueberry muffins, snow goose casserole with wild rice – all prepared from treasured family recipes using tundra ingredients. And after stuffing our faces, we sink into armchairs by the wood stove to enjoy the view outside: the constant play of light and tide; the slow-burn slideshow of clouds, sunsets and rainbows.
This summer window is a brief one. Mike's stories and photos make me long to return in winter, to witness the bay freezing over and the tundra blanketed in white. Even now, the season hints at change: on our final hike, we spot snow geese overhead and caribou prints underfoot, outriders of the great migrations that will soon be passing this way.
Our last morning finds our inflatable boat crossing the bay towards Hubbard's Point, a remote spit some 15 miles north of the lodge. As the Zodiac skims through the water, belugas surface dazzling white in the channel beyond, and a single bear lopes away from our approach. We scramble up seaweed-strewn rocks onto a promontory littered with old beluga bones. Some were stranded there, explains Andy, others killed by bears.
But bears may not have been the only killers. Further inland a loose stone circle is more than arbitrary geology: this is a tent ring – the stones arranged where they once anchored the walls of an Inuit tent. Who knows how long they've been here. For centuries the Inuit roamed this area, following the caribou and hunting belugas when the ice permitted. It's a reminder that this harsh land was once a home for people, too. People made of sterner stuff than I am.
Travel essentials: Manitoba
* The writer was a guest of Churchill Wild (001 204 377 5090; churchillwild.com) on the "Birds, Bears and Belugas" tour, which includes one night in Winnipeg, one in Churchill and five at Seal River Heritage Lodge. The seven-night trips cost C$8,475 (£5,311) per person full board with internal transfers but excluding international flights.
* The "Birds, Bears and Belugas" itinerary is also offered by Windows on the Wild (020-8742 1556; windowsonthewild.com), from £5,935 per person including flights from London.
* The writer visited Hudson Bay courtesy of Travel Manitoba (001 204 927 7838; travelmanitoba.com), Travel Winnipeg (001 204 943 1970; tourismwinnipeg.com) and the Canadian Tourism Commission (0870 380 0070; canada.travel).
* There are no direct flights between the UK and Manitoba. You can fly to Winnipeg from Heathrow via Toronto with Air Canada (0871 220 1111; aircanada.com).