In search box put in the area you are searching for. I put in "Congo" and received the following ecoregions of Congo River and hyper-links to look at each of these areas more indepthly.
Ecoregions
Major Habitat Type
Ecoregion
535 Afrotropic Tropical and subtropical floodplain rivers and wetland complexes
Sudanic Congo - Oubangi
539 Afrotropic Tropical and subtropical floodplain rivers and wetland complexes
Upper Congo Rapids
540 Afrotropic Tropical and subtropical upland rivers
Upper Congo
549 Afrotropic Tropical and subtropical floodplain rivers and wetland complexes
Lower Congo Rapids
550 Afrotropic Tropical and subtropical floodplain rivers and wetland complexes
Lower Congo