The trunk of her car ajar, a young brunette is found slipping into a wetsuit, while her boyfriend waxes their boards on the banks of the river, some 500 kilometers (300 miles) inland from the Atlantic Ocean.
A few years ago, they might have been described as mad.
But today, surfing at this spot has become commonplace, attracting hordes of wave junkies over the past five years from Munich, Geneva, Turin and Lyon.
Neighbors no longer mind them squatting in their parking spots, taking joy instead in watching their water acrobatics on waves as high as 1.5 meters (five feet).
"It's becoming more and more popular. There's always people here. On weekends, you sometimes have to wait up to 45 minutes for your turn on a wave," local surfer Simon Rouleau, 24, said.
Unlike ocean waves or swells on rivers such as the Amazon in Brazil caused by sudden drops in elevation, the waves on the Saint Lawrence are steady, caused by a jagged riverbed.
"It's incredible in Montreal, the waves are always there," Corran Addison, a pioneer of surfing here, told AFP.
The South African three-time kayak freestyle world champion says he was the first to have tamed the mighty Canadian river seven years ago.
He says he moved to Montreal to surf at this spot 365 days a year, even in frigid winter months when floating sheets of ice drift past and temperatures drop below minus 20 degrees Celsius (-4 Fahrenheit).
"I wake up in the morning and I don't have to think about ocean tides, storms, the weather... if I feel like surfing, I go surfing... the wave is always there," said the 40-year-old.
After making converts of his friends, Addison went all out and started a surfing school here in 2004. A second rival school opened shortly afterwards. Together they attract about 2,000 students each year.
Some 500 surfers now regularly descend on this spot, many novices, but also some accomplished surfers hardened by big ocean waves.
This is the case with Robert Smyth, a 59-year-old Australian whose surfboard was gathering dust ever since he landed in Canada in 1972, until now.
"When I was young, I surfed using longboards in Australia... it's very different here but it's still a lot of fun," he said.
The Sydney native appreciates that he does not have to swim out to catch a wave. It is enough to just point your board in the right direction, drift from shore into a wave and leisurely stand up.
"I don't even have to paddle... I'm too old for that anyway," he quipped, sporting a safety helmet in case he bumps into some rocks.
Such surf requires specialized equipment: a solid board, for example. The nascent market is, however, mostly ignored by the large surfboard makers, which has given Addison's own brand 2imagine a leg up.
This year, 1,000 of his "Made in Montreal" surf boards were sold worldwide.