The warm North Brazil Current moves east-to-west across the river's outlet, carrying turbid, fresh water to the northwest towards the Caribbean Sea.

This deep reef is colonized by sponges and other filter feeders, under conditions of low light and dense particulates.

The NBC is additionally fed by the outflow of the Amazon River, lowering the salinity and raising the turbidity of the water through the Amazonia marine area.

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) during the winter months, then slacks off somewhat in the summer as the Intertropical Convergence Zone (ITCZ) shifts north.

The inlets, swamps and lagoons provide shelter, food, and breeding habitat for birds, invertebrates and fish.