According to the Tidal Bore Research Society, this rare phenomenon is only found on 55 waterways. It is a wonder that has never been truly understood, even though predicting a bore wave's arrival and size is fairly easy. Unlike ocean waves, the bore has two currents: one at the top pushing ahead and another one below from the downstream river flow. At times, the mighty bore has wreaked great havoc on riverside infrastructure and last century several majestic bores were stripped of their power by human intervention. The word pororoca comes from poroc poroc, which means destroyer, big-bang, in the regional aboriginal dialect and the phenomenon was first shown on Brazilian TV after Jacques Cousteau aboard the Calypso first shot the phenomenon on the 28th March, 1982. It was breaking 15km (9mi) out to sea, outside the Araguari rivermouth, at about 10ft (3m) high and going 45 km/h (30mp/h), before they followed the bore 25km (15mi) upstream. In 1997, a country known for small waves became the Hawaii of the bore-riders with pioneers like Noelio Sobrinho, Guga Arruda and Eraldo Gueiros taking on the pororocas. The huge Amazon basin fed by a dozen rivers proves to hold the longest rideable waves on earth and in April, 2003, an unofficial world record was set. Picuruta Salazar managed to ride the bore for 37 minutes and travel 12.5km (7.8mi) before Serginho Laus, on 24th June 2005, and in the presence of an official Guinness adjudicator set the new distance surfing world record with a 33 minute ride of 10.1km (6.3mi). Since 1999, an annual championship has been held in São Domingos do Capim and there is now frequent events on Rio Araguari or Rio Mearim.