From http://fogonazos.blogspot.com/2007/03/pororoca-surfing-amazon.html .....

The name "Pororoca" comes from the indigenous Tupi language, where it translates into "great destructive noise". The wave can be heard about 30 minutes before its arrival, and it's so powerful that it can destroy anything, including trees, local houses and all kind of animals.
The wave has become popular with surfers. Since 1999, an annual championship has been held in São Domingos do Capim. However, surfing the Pororoca is especially dangerous, as the water contains a significant amount of debris from the margins of the river (often, entire trees).
The record that we could find for surfing the longest distance on the Pororoca was set by Picuruta Salazar, a brazilian surfer who, in 2003, managed to ride the wave for 37 minutes and travel 12.5 kilometers. A surfer’s dream: riding an almost never-ending wave.