Nearly 20 mouths reach the sea here. The two main ones are the Nun and the Forcados. The outer delta is fronted by a zone of sandy beaches backed by mangrove swamps and creeks. Inland, towards the head of the delta the vegetation changes to freshwater swamps and dense forest.

The Niger has been building this delta since the breakup of of the super-continent, Gondwana, although a large part of the sedimentary deposits have been laid down in the last 12,000 years. It is thought that the deposits laid down here are more than 10,000 metres deep!

The Niger is Africa's third longest river at 4,185km long. It rises in the highlands of the Fouta Djallon Plateau in western Guinea, 240km from the Atlantic Ocean, and flows northeast into Mali. In central Mali, the Niger forms a vast inland delta, a maze of channels and shallow lakes.

The river continues through the Republic of Niger and on into Nigeria where it is joined by its chief tributary, the Benue. The Niger then proceeds south 400km before becoming a great fan-shaped delta and emptying into the Gulf of Guinea.