Surfers line up and take turns slipping into a perfectly formed wave, popping up on their boards and carving through the clear blue water.
It's a familiar scene on the balmy beaches of Australia, Hawaii or South Africa, but this is a frigid November afternoon in Alberta's Rocky Mountains.
It's called "river surfing" and it's a growing trend for surfers around the world who don't happen to live close to an ocean.
Neil Egsgard, leader of the Surf Anywhere group that built this wave on the Kananaskis River, says it's one of the best "inland waves" around.
"Right now, it's the best wave that's working in the world, the best wave in Canada for sure."
It took Egsgard about a decade to get the permission and the time needed to build this wave on public land about an hour west of Calgary, a process that involved placing boulders in the river to form a channel.
"It cost about $25,000 cash, with enormous amounts of donated time and expertise and many tens of thousands of dollars of donated material," he says.
"Building a good wave for $25,000 is an incredible achievement. River waves historically cost between $200,000 to millions."
The result is a permanent wave that surfers can ride for free, without actually moving along the river.
"It needs to be fast, it needs to be powerful and it needs to be smooth," says Egsgard.
Hot waves in cold water
Jacob Kelly Quinlan stands shivering in a snow bank as he tugs on his wetsuit. Quinlan is something of a river surfing aficionado, having surfed more than 50 rivers from Germany to Oregon, and says Calgary is now a hub for the sport.
"This is one of the central points for river surfing culture around the world," he says.
Quinlan, who also teaches river surfing, says the sport is similar to traditional ocean surfing, but with a twist.
"The guys on the shore are watching you surf and it doesn't look like you are going anywhere," he says.
"When you're out there on the wave, everything is moving so fast. It feels like you're going a million miles a minute."
However, Quinlan admits surfing on a river comes with its own challenges.
"You're going to hit some rocks," he says.
"I have taken definitely some knees and shins, and bounced off the bottom a couple of times."
But that potential pain isn't preventing the sport from growing, as more and more people like Julia Barnes catch their first inland wave.
Barnes, who runs a Calgary-based surf-wear company, says riding a wave next to snowcapped mountains is almost too good to be true.
"It's pretty magical. I don't think any real surfers, ocean surfers, can say the same, so this is quite amazing."