By Michael Astor
Helio Noelio Sobrinho had been surfing for years off Brazil's northern seacoast when he discovered The Wave.
It was a surfer's dream - a wild, dangerous, seemingly endless ride unlike any he had ever known. It wasn't even in the ocean.
It was the "pororoca", a Tupi Indian word meaning "great noise". It happens briefly around the full moon in February and March, when the ocean whips back on the heavily drained Amazon River and creates a gigantic swell which flows back upstream for hundreds of kilometres.
Always preceded by a dark storm cloud and a short brisk rain, the pororoca resembles a horizontal tornado as it thunders upriver through the rainforest. Swells as high as three metres can run for 45 minutes, wrenching aninga palms from the riverbanks and overturning boats or tossing them into the jungle.
Amazon residents have ridden the pororoca for years in their canoes, and French oceanographer Jacques Cousteau once lost much of his equipment trying to film it. Surfing it was just a question of time.
"The minute I saw it, I knew it could be surfed," said 33-year-old Noelio, who first rode the pororoca in 1997.
"But I was so busy figuring out how to ride it, I forgot to get someone to take my picture. So everyone called me a liar when I told them I did it and I had to wait a year to prove it."
The first Pororoca Surf Championship
Noelio went further, organising the first annual Pororoca Surf Championship in 1999. The event drew professional surfers from across Brazil to this poor jungle town about 145km from the mouth of the river.
This year, the competition was held between March 9 and 13 - three days for the actual championship plus two days in case the wave didn't show up on time.
"It's still an alternative event in the world of surfing, but there is a lot of interest because it's the closest you'll ever get to an endless wave," said Sergio Laus, 21, who writes for the Brazilian surf magazine Hardcore.
Similar phenomena occur on China's Qiantang River, Canada's Bay of Fundy and on the Severn River in England.
Laus said he's heard of people surfing the Severn bore, but Brazil has the world's only organised river surfing competition.
The hazards of river surfing
The rules were adapted for the wave's longer duration and other peculiarities of river surfing.
For example, surfers have to catch and recatch the wave from jet skis or motor boats - if they miss it, the next one might be hours or even months away.
Competitors say it's harder to surf in rivers than in the ocean because the water contains none of the salt that helps keep things afloat at sea. Even with extra-thick boards to add buoyancy, surfers have to work constantly not to sink.
"It's different from ocean surfing because the intensity of the wave is always changing. When it's weaker, you have to really work just to keep it," said 26-year-old Sandro Rogerio de Sousa, last year's champion.
There are other hazards. The wave picks up enormous logs and other jungle debris as it rolls along, and a wipeout can put a surfer in the middle of them.
The pororoca also can suddenly split off and sweep far into the jungle up one of the Amazon's many tributaries.
As if these obstacles are not enough, surfers
have to worry about alligators, anacondas, piranhas and the dreaded candiru - a tiny fish which, legend has it, swims up the human penis and lodges its spiny fins in the flesh so firmly that removing it usually requires amputation.
That hasn't dampened interest in the annual event.
"There's nothing that compares with it," says Ricardo Tatui, 33, a former national surf champion from Rio de Janeiro.