The marine ecoregion extends from the mouth of the Parnaíba River in the west around the eastern point of the Brazilian mainland and south to the Bay of All Saints.

The bordering coast is low and flat, and characterized by mangrove forests, such those of the Rio Piranhas mangroves terrestrial ecoregion,[7] and the flat plains of the Zona da Mata on the east coast.

The continental shelf along this coast of Brazil does not extend far into the sea, typically dropping off onto the slope at about 30 miles.

[8][9] The NBC flows at a rate averaging 26 Sverdrups (Sv), at a mean speed of 60–100 centimetres per second (1.3–2.2 mph).

The commercial fishery is centered on shrimp, lobster, and southern red snapper.