The Rio Araguari is the largest river in the interior of Amapa state, independent from the main Amazon basin. It's source is high in the western Tumucumaque mountain range. From here it flows approximately 350 km south and east, collecting the waters from many of the state's other rivers. Finally the Araguari drains into the Atlantic ocean at the northern end of the mouth of the Amazon, just south of Cape Norte.
The Araguari pororoca is possibly the most feared of all the Amazonian tidal bores. The vast extent of the river's sedimentary basin stretches so far into the Atlantic, that the bore has apparantly, and uniquely, been observed breaking 10 km out to sea.
Observing the Araguari pororoca is not easy, and takes a long boatride or viewing from the air. The pororoca is observable for about fourty minutes breaching approximately 25 km inland, and since 2001 has become the home of the most extreme tidal bore surfing.