It covers an area of approximately 4,940 ha (49.4 square km) and encompasses a range of types of wetlands and vegetation, from freshwater marsh to sand spits and brackish lagoons.

[2] Niumi National Park occupies the coastal strip in the southern tip of the Sine-Saloum Delta.

It encompasses a range of types of wetlands and vegetation, from freshwater marsh to sand spits and brackish lagoons.

Many species found in the park are vulnerable or endangered including the green sea turtle, humpback dolphin, red colobus and West African manatee.

The park has been designated an Important Bird Area (IBA) by BirdLife International because it supports significant populations of non-breeding and wintering slender-billed gulls, and Caspian, Sandwich and royal terns.