River surfing is different than regular surfing, but only in duration. The sport consists of riding a stationary wave in a whitewater river as long as you can stay on your feet. The form is the same, but the ride's longer, and you’re not going anywhere.

"You could conceivably have an hour-and-a-half-long ride," says Corran Addison, a San Clemente-based board maker who spent years on Montreal's St. Lawrence river.

A naturally occurring dip in a river’s grade or an underwater obstruction such as a rock shelf folds water back on itself, churning up a standing wave. In fact, most whitewater rivers have surfable waves, but you're unlikely to see surfers on them. Getting to the break can be difficult and the sport requires specialized equipment. Serious river surfers use a shortboard around six feet long and leap onto their wave from a nearby boulder in order to generate enough speed to stay upright. Failure to stand up quickly means a long and bruising swim through the whitewater.

The sport, first practiced on Jackson Hole's Snake River in the seventies, has gained popularity recently – largely thanks to viral videos. Here are the best places to try it out.

Bend, Oregon

Though it sits almost 4,000 feet above sea level, Bend is the world's river surfing capital thanks to a smattering of rapids along the Deschutes River and the agricultural canals outside city center. The waves are big, consistent, and cold. Bring a wetsuit.

Montreal, Quebec

The St. Lawrence River cuts a broad swathe through the center of the French-speaking party town, but just outside - near the famed Habitat 67 apartment buildings, a permanent wave rolls under Quebecois carvers. Getting to the break is easy. Staying in the water can be tricky if it isn't summer.

Zambezi River, Zambia

Just downstream from Victoria Falls, the Zambezi's rapid number 11 offers surfers a consistent wave in the thick of whitewater fierce enough to keep the crocodiles at bay. Kayak the Zambezi, a local outfitter, runs trips.

The Dordogne River, France

Called "Le Mascaret" by locals, the largest tidal bore on the Dordogne attracts serious surfers to wine country. Unlike other river waves, the Mascaret moves, making it the ultimate way to travel through one of France's most scenic regions.