Surfing was first practiced by the ancient Polynesians. Early surfers rode heavy boards made from large trees and practiced their craft as an art and religion — if the surf was bad they would call upon the surf gods to kick up the swells. Europeans made first contact with surfing in 1767, and as they were wont to do, promptly starting banning natives from practicing it.

Surfing was kept alive by a small line of devotees in Hawaii until 1907, when George Freeth traveled to California to show off the sport. It hit the East Coast of the U.S. in 1912 when it debuted in Virginia Beach, Va., and landed in Australia just a few years later in 1915.

Today there are tens of millions of surfers around the world and surfing has become a multi-billion-dollar industry. Surfers are continually on the hunt for the next great wave, and some have turned to unconventional places to get their fix. From river tidal surges to the wake of a giant tanker ship, if there is a wave to ride, there's someone who wants to ride it.

Here are nine videos of people surfing in unconventional places.

Tidal bores

Tidal bores occur when the water from an incoming tide travels up a river or narrow bay against the flow of the river or bay's current. The tidal water can form a wave that travels up the river at speeds up to 25 mph. Surfers ride tidal bores all over the world, but if you want to find the biggest and fastest bore, you head to the Qiantang River in China, where bore waves can top 25 feet high.

If riding with piranhas is more your style, you can head south and ride the Amazon tidal bore.

Houston Channel tanker wake

Modern day transport ships are huge. The skyscraper-tall ships' massive propellers plow them through the water at a slow but steady course, leaving behind a large wake that, in some instances, is ridable by surfers. The Houston Ship Channel leads into the Port of Houston, one of the United States' busiest sea ports, and sees many very large ships travel its length every day. This video is beautiful in its simplicity. You almost miss the surfer, who appears to be riding without the benefit of a tow-in partner driving a boat.

Where the kayakers paddle

Play boat kayakers like to find one section of a whitewater river and then take turns playing in on the static waves. In Montreal, Canada, surfers have found places on the St. Lawrence River where they can catch rides all day long. They get as much surfing in in a day as an ocean wave rider does in a month.

The FlowRider 

The FlowRider generates an endless wave by shooting a high flow of water up and over a smooth curled up wall. It offers both a beginner-friendly taste of the thrills of riding the waves as well as a platform for pro riders to push the boundaries of what's possible. Flow boarding is quickly becoming its own sport with specialized tricks and competitions. Here's video from a 2009 flow boarding contest in Hawaii.

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Thumbnail photo: mikebaird/Flickr