Twice a year, between the months of February and March, the Atlantic Ocean waters roll up the Amazon river, in Brazil, generating the longest wave on the Earth. The phenomenon, known as the Pororoca, is caused by the tides of the Atlantic Ocean wich meet the mouth of the river. This tidal bore generates waves up to 12 feet high which can last for over half an hour.
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 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.