The phrase tidal bore sounds like a euphemism for a long-winded oceanographer. As it turns out, however, tidal bores are massive waves created when the tug of the moon pulls the ocean into the mouth of a river. The incoming tide hurls the river back on itself, squeezing into an ever-narrower space to create a giant swell that rumbles upstream for miles before dying out. Tidal bores occur everywhere from the Bay of Fundy to the Qiantang River in China. But few are as fast or furious as Brazil's pororoca, a deafening collision between the Atlantic tide and the Amazon. The pororoca-the name means, roughly, "big roar" in the native Tupi Indian dialect-hurtles up the world's biggest river once a night and once a morning for four days around the spring equinox. Two miles wide and up to 13 feet high, this mocha-colored wave churns up mud, uproots trees and gouges out farmland at the river's edge while surging at speeds of up to 20 mph. You can hear the pororoca's chocolate thunder 40 minutes before it actually reaches you.
Locals have long navigated the powerful current in their canoes. But it was surfers who turned the tidal phenomenon into a cutting-edge adventure destination. They began riding the bore in 1997 and holding tournaments on it in '99. Last year saw the inaugural pororoca world championship. On the pro surfing tour, a decent Atlantic roller lasts maybe 30 seconds. The pororoca, on the other hand, seems to go forever. Brazilian surfer Alex Salazar claims the unofficial record for the most time on a wave: 37 minutes.
For sheer maneuverability, kayaks are actually better suited to riding the wave than slivers of fiberglass are. "Way better suited," says Steve Fisher, a 29-year-old South African widely acknowledged as the world's top all-around kayaker. "Then again, when things go awry on a board, you just jump off." It's not so simple in a kayak.
Earlier this month Fisher and five buddies became the first kayakers to tackle the pororoca. They braved close encounters with all manner of jungle debris dragged along by the wave-canoes, sheep, cattle, and logs the size of phone booths. The list of potential hazards included crocodiles, anacondas, bushmasters, sharks, piranhas, stingrays and whirlpools, which tend to swallow capsized boats whole and spit them out half digested.
Until now, kayakers had been limited to two types of surfable waves: the ocean variety, in which the wave moves and the water is stationary; and the river variety, in which the wave is stationary and the water moves. "Both start as gentle swells, rise up, peak, and lose intensity when they break," Fisher says. "The pororoca is unique. Its energy is constantly regenerated by the enormous mass of water propelling it."
The kayakers woke up each day at 3 a.m. to meet the pororoca at dawn. To catch the wave, they launched themselves from motorboats in front of its rising lip. "Watching the shore pass you as you head upstream is a wild feeling," says Rusty Sage, winner of the 1998 freestyle preworlds and the lone American on the expedition. "You've got lots of room to move around and gun down the wave's face."
He and the guys tried just about every trick in the book, from kamikaze backstabs to hara-kiri helixes-those breathtaking innovations of Fisher's that involve an inverted spin and a complete barrel roll. About the only move they didn't try to pull off was the aerial coup de th��ter known as an airscrew. "We had the wrong boats for that one," says Sage.
The movements of the pororoca are unlike any ocean swell's. "It's important to know how to read the wave," Sage says. "The pororoca changes both direction and speed." Tracing the ever-shifting river bottom, the bore can suddenly veer off and plow far into the rain forest up one of the Amazon's many tributaries. "At some point the wave is going to crash on the shore," Fisher says. "And nobody wants to wipe out on a mud cliff at 25 klicks [15.5 mph]."
The diciest moment came on Day Two, when one of the motorboat pilots ran aground on a sandbar just as the pororoca barreled in. Everyone jumped out of the boat and pushed it to a deeper channel. "It was mass panic," recalls Sage. "In the confusion the fuel line was knocked off the engine." When the engine wouldn't start, the kayakers paddled away. The motorboat pilot got swamped. He held onto the steering wheel so tightly that it broke off in his hands.
Sage's greatest fear was not snakes or crocs or even floating timber. "It was candir�," he says. The toothpick-shaped one-inch-long catfish can follow the scent of urine up a victim's urethra, where it anchors itself by flaring its spiny fins. The pain is said to be spectacular; the trick is to get to a hospital before your bladder bursts. In case you were wondering, one extreme method of removing a candir� is penile amputation.