Almost all of Guinea-Bissau is low-lying and bathed daily by tidal waters that reach as much as 62 miles (100 kilometres) inland. In the southeastern part of the nation, the Fouta Djallon plateau rises around 600 feet (180 metres). The Boé Hills extend from the western slopes of the Fouta Djallon to the Corubal Basin and the Gabú Plain.The coastal area is demarcated by a dense network of drowned valleys, called rias. The Bafatá Plateau is drained by the Geba and Corubal rivers. The Gabú Plain occupies the northeastern portion of the nation and is drained by the Cacheu and Geba rivers and their tributaries. The interior plains are part of the southern edge of the Sénégal River basin. The uniform elevation of the mature floodplain allows rivers to meander and renders the area susceptible to flooding during the rainy season.

The population of Guinea-Bissau is ethnically various with distinct languages, customs, and social structures. Most people are farmers, with orthodox religious beliefs; 45% are Muslim, principally Fula and Mandinka-speaker concentrated in the north and northeast. Other valuable groups are the Balanta and Papel, living in the southern coastal regions, and the Manjaco and Mancanha, occupying the central and northern coastal areas.