There’s only one place in the world where you can watch hundreds of beluga whales cavort in the wild, their gleaming white bodies arching above the surface of the water. That place is Churchill, a small town in northern Manitoba where the population of less than a thousand people is diminishing, but not the number of whales.

Some 20,000 beluga whales populate western Hudson Bay and the Churchill River estuary, which meet at the lip of land bordered by the town. Of those, 3,000 whales spend the summer at the mouth of the river, feeding on French fry–sized capelin and cisco.

From land, they look like sandbars or whitecaps. But when you look closely, you realize you’re seeing hundreds of magnificently smooth, white beluga backs glinting in the sun as the animals surface briefly for air before diving again.

They come to the Churchill River in August to give birth to their young, because the marginally higher temperatures there place less stress on the calves. By the middle of August, there’s a grey-brown baby beluga in every pod, following its mother like a ghostly shadow, its colour fading to grey-blue and then to white as it matures.

I’ve come to Churchill to see them for myself. To get a better view, I don a head-to-toe seven-millimetre-thick wet suit, grab a snorkel, and try to build up the nerve to slip off the side of a Zodiac and into the Churchill River.

I’ve been warned that the water is shockingly cold, but nothing could have prepared me for the chill that sinks straight into my bones, numbing my head like a prolonged ice-cream headache as I clutch the rope that will tow me gently alongside the boat.

At first I see nothing but a great stretch of blue-green vastness, with the occasional jellyfish floating by. Then suddenly they are below me: a pod of beluga whales swimming gracefully through the water.

Initially, they stay a cautious five metres away. But after half an hour with people in their presence, they get friendlier, their bodies arching closer to the vessel and the snorkellers it is trailing.

They are spectacular to watch, these gliding, four-metre-long mammals that can live as long as 30 years and dive to depths of 600 metres without harm from the cold.

Transfixed by the eerie beauty of this underwater world, I’ve forgotten the discomfort of the 6 ° C water, and I am only too happy to stay submerged despite the pelting rain on my back and the strength of a current that’s trying hard to pull me away from the Zodiac.

Sound is everything to these mammals, whose chirping and shrill, sea gull–like calls have earned them the nickname “canaries of the sea”. I start to hum in the water, feeling a tad sheepish, and I soon find myself face to face with a 2.5-metre-long beluga.

Its mouth upturned in a perpetually impish grin, this graceful giant turns its head briefly to get a better look at me. Releasing a balloon of bubbles that cascades up toward my face, the beluga slips playfully from its stomach to its back, and then, with a barely visible movement of its tail, it’s gone.

Around, beside, and below me, white shapes continue to emerge from the depths, silently and with unmistakable playfulness. Belugas are the only whales with movable neck vertebrae, which means they can turn their heads to inspect us.

As recently as the 1970s, they were hunted for sport and commercially as food for mink farms. Today they are still hunted, particularly in western Greenland, but the mammals that surround us now clearly feel no fear.

Perhaps they know that they can far outlast us in this water. It’s just a matter of time before we clamber, shivering, back into the Zodiac and the freezing wind and head for land.

Some of the belugas have harpoon scars that attest to a lucky getaway; others sport the claw marks of a polar bear that just missed his prey. In the Churchill River, they can frolic in relative safety from their main predator: orcas.

“The orcas come late in the season,” says Mike Macri, owner of Sea North Tours, which runs the Zodiac tours. When the belugas hear predators in the distance, they flee to water as shallow as four feet, where they know they are safe. But as the onset of winter draws closer, and with it the inevitable freeze-up of the river, they must migrate into the Hudson Strait, where they can surface to breathe.

As the belugas stream into the deep water of Hudson Bay for the winter, the orcas, which can move three times faster than their prey, attack them in groups. “Last year, I saw seven orcas in the bay,” Macri says. “No one knows how many belugas they claim, but I know they got some, because I saw a polar bear swimming away with a chunk of beluga meat.”

I wondered how snorkelling with the mammals affected them, so I call up Pierre Richard, a marine-mammal research scientist with Fisheries and Oceans Canada’s Arctic aquatic research division. He says that from an environmental standpoint, snorkelling with belugas is a pretty innocuous activity.

“I don’t see why it would cause any impact to the whales, because they are easily able to evade snorkellers if they don’t feel comfortable,” he says. “For the most part, the belugas in Churchill are quite curious about people and approach them readily.”

Pete Ewins, director of species conservation at World Wildlife Federation Canada, says that any concerns about snorkelling with belugas should centre around orcas.

“As ice melts and climate change proceeds in a runaway state, there’s a lot more killer whales coming into the Arctic in the summer, and they’re changing the behaviour of narwhals and belugas,” he explains by phone from Toronto. “At some point, those hungry killer whales may come across snorkellers, and from that point of view, there could be some risk.”

Back in Churchill, I walk through town and find myself on the pebbled beach that borders the Churchill River. The sun has come out, and on a glorious August afternoon I’m treated to a view of hundreds of belugas as they play in the shallows.

Churchill is the final stop on a railway line, and as global warming steadily depletes the number of polar bears—Churchill’s star attraction—the town has a dubious future. But on this beach, with belugas just a few feet away, the world still looks promising.

Access: Sea North Tours offers snorkelling excursions as well as the opportunity to view belugas by boat and use a hydrophone to capture their sounds. For information, see www.seanorthtours.com/. Calm Air (www.calmair.com/), Kivalliq Air (877-855-1500), and VIA Rail (www.viarail.ca/) offer access to Churchill. The writer travelled as a guest of Tourism Manitoba (www.travelmanitoba.com/).