The pororoca is a tidal bore, with waves up to 4 meters high that travel as much as 13 kilometers inland upstream on the Amazon River. Its name comes from the indigenous Tupi language, where it translates into "great destructive noise". It occurs at the mouth of the river where river water meets the Atlantic Ocean. The phenomenon is best seen in February and March.

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 shores of the river (often entire trees). In 2003 the Brazilian Picuruta Salazar won the event with a record ride of 12.5 kilometers during 37 minutes.