The pororoca is a tidal bore up to 4 meters high that travels upstream 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, where waves up to 4 meters rolling for up to 35 minutes have been observed.

The wave has become popular with surfers. Since 1999, an annual championship has been held in Sao 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).