Pororoca

thumb|Pororoca near the mouth of the Araguari River (Amapá)|Araguari River, seen from an airplane The Pororoca (, ) is a tidal bore, with waves up to high that travel as much as inland upstream on the Amazon River and adjacent rivers. It occurs at the mouth of the river where its waters meet the Atlantic Ocean. It can be observed from the islands Marajó and Caviana, and in various rivers of the state Pará.

==Etymology== Its name might come from the indigenous Tupi language, where it could translate into "great roar". It could be also a Portuguese version of the term poroc-poroc, which in an indigenous' language was a way of expressing the act of destroying everything. It could be also a portmanteau of the words poroc (to take out, to tear away) and oca (house).