"We all live in a yellow submarine, a yellow submarine, a yellow submarine..."

As I gurgle the Beatles' classic through a snorkel, I wonder what the Fab Four would make of their lyrics being used to attract the attention of beluga whales.

Face down, my legs looped through a long rope tied to a Zodiac boat, I rattle through a repertoire of cetacean-inspired songs, as I'm dragged like bait along the Churchill River.

Licence To Krill; Ba-leen On Me; He Ain't Heavy, He's My Blubber - bad puns are at least a mild distraction from the numbing 5C water temperature.

Every year, from June until September, 59,000 beluga whales congregate in Canada's Hudson Bay to feed on capelin fish; the world's largest gathering of the whale species. Several operators have realised the enormous potential for tourism, and word is slowly spreading about the range of beluga-related activities on offer.

Dressed in dry suits, we head out at high tide, when ocean water from the Hudson Bay supposedly makes the river clearer.

I hear them first, a high-pitched clicking sound, as if the dial has suddenly slipped onto Radio Whale.

White shapes appear through the murky, tea-coloured water, like ghostly apparitions diving in and out of focus. They soar underneath me, flipping over to get a better view, and even twist their necks (thanks to flexible vertebrae), before vanishing in an explosion of bubbles.

Belting out my song list, at times it feels like we're duetting, and given the apparently permanent grins etched on their faces, I can't resist imagining these ebullient creatures are enjoying themselves just as much as I am.

Hudson Bay's gateway town, Churchill, is best known as the Canadian Arctic's polar bear capital, where hundreds of marine mammals gather on the frozen freshwater in September. A two-and-half-day train journey across barren prairies from Manitoba's capital Winnipeg (or a two-hour flight), it sits at the end of the track, on the tip of the tree line, with only wilderness beyond.

Once a thriving port and military base, this frontier town has slowly been abandoned - just like the wreckage of a C-46 twin-engine plane nicknamed Miss Piggy, which crash-landed here in 1979, or the Ithaca, a rusty shipwreck from the Fifties, which sits on a mudflat and can be accessed at low tide.

Since the 1970s, when urban myth suggests an entrepreneur kick-started polar bear tourism by ferrying people around on a Lazy Boy strapped to the back of a truck, Churchill has become a bit of a circus, a victim of it's own popularity.

But in summer, it's quieter - yet there's still so much to see.

Clusters of chamomile flowers and microscopic orchids flourish from every possible rocky crag, and at night, there's just enough darkness to catch a faint outline of Northern Lights.

Clouds of black midges are less appealing, and after two days, my backside resembles a firing target, peppered with failed attempts to hit the bullseye.

The bugs don't seem to bother wildlife guide Wally Daudrich, who came here in 1980 and opened his log cabin, Lazy Bear Lodge, five years later. Made with fire kill wood (leftovers from trees destroyed by forest fires) and reclaimed items, such as flooring from an 1800s railroad building and window frames once belonging to a Hudson Bay Trading Company warehouse, it took a decade to build.

Now self-sufficient, Wally runs his own operations, meaning he doesn't have to rely on third parties for heavily weather-dependent activities to go ahead.

Guests, like me, can book snorkeling or kayaking trips depending on the tides, with re-arrangements rapidly made if a storm draws in.

Heavy fog, though, isn't enough to deter us from an early morning kayak with the belugas. Pale humps bob in the water like the white crests of waves, as I paddle alongside a ghostly skeleton of the port. Watery shadows appear alongside me, and suddenly I glide along effortlessly, as three belugas join forces to push me from the rear. I prefer to believe the whales are trying to help me rather than capsize my kayak, as one cruel cynic suggests.

In reality, little is understood about beluga behaviour.

"Being such a common species, research work has always been deprioritised," says Stephen Petersen, head of the International Polar Bear Conservation Centre in Winnipeg.

But in July, the department of Fisheries and Oceans Canada tagged several of the Churchill River beluga community with assistance from Stephen and Lazy Bear Lodge. They hope to track their journey over the next 12 months, with progress followed on a Twitter feed (@ArcticWhaleRes).

At present, there are no official guidelines regarding the conduct of beluga tourism - although there have been murmurings of introducing a minimum distance rule - but Stephen believes current visitor levels are low enough not to have any impact.

He does recall an unsuccessful sonic art show involving a concert being performed underwater for the aurally sensitive whales. "They didn't really like it," he says, laughing, before lamenting the fact it's easier to get a grant for a leftfield art project than for scientific research.

Much more is known about the Churchill polar bears, who are increasingly sticking around on land for the summer months.

Wally has built his own boat, the Sandpiper, to look for bears at Hubbard Point, an area otherwise only reached by helicopter. But many of the apex predators come closer to the town (which lies on their migratory path north), as I discover on a stroll along the beach.

Distracted by waves pummelling the smooth quartzite rocks unique to this coastline, I fail to notice the mother and two cubs a heart-pounding, pant-wetting and life-evaluating 50 metres away from me. Fortunately, I spin around to see three bulbous bottoms heading in the opposite direction, sashaying along the shoreline like calypso queens.

Within seconds, the Polar Bear Alert Team has arrived, firing blanks to scare the bears away. Any problem animals might wind up in D20, the local "bear jail", where they'll remain until they can be safely transferred to more remote wilds.

But in the summer, polar bears do little more than laze and languish, trying to conserve vital energy in a state of semi-hibernation.

Eager to spend more time with Churchill's stupefied outlaws, I enlist the help of Jen and Gerald from Bluesky Bed & Sled, a couple with an endless love of wildlife, who famously trained the world's first blind sled dog.

With long, wiry hair, a handlebar moustache and a rifle slung over his shoulder, Gerald is well equipped to handle any potential bear confrontations.

We jump on a quad bike and hurtle across the springy tundra, through tufts of purple fireweed now coming into bloom. Soon we find a bear polishing off the remains of a whale, while a bald eagle hovers closely, hoping for scraps. Further along the beach, where boulders glow orange with lichen, we discover another ursus maritimus, crouched in the sea and surrounded by crashing waves. A long blue, flaccid tongue trails over her lower lip, as she pants like a dog to keep cool.

We quietly sit at a safe distance, and an afternoon spent sunbathing with polar bears turns out to be unexpected bliss. Even the sores on my bottom do little to stop me smiling; I leave with a grin even bigger than a beluga's.

TRAVEL FACTS

:: Sarah Marshall was a guest of the Manitoba tourist board.

:: Lazy Bear Lodge (www.lazybearlodge.com) offer the Ultimate Arctic Summer Adventure every July and August for 3,285 CAD with domestic flights originating in Winnipeg and six nights accommodation.

:: Air Canada (www.aircanada.com) flies to Winnipeg via Toronto from London.

:: For more information on the destination, visit www.keepexploring.ca and www.everythingchurchill.com