The waterways of Niumi are home to the regions rare aquatic mammals, the West African Manatee and African Clawed Otter.
The Atlantic Humpbacked Dolphin also utilizes the Niumi waterways and coastal waters.
The sand shoreline between Barra and Buniado Point on the island of Jinack is used by nesting Green Turtles, a species that has suffered alarming declines in the last few decades (Eckert et al, 1999).
Nile Crocodiles are found in both permanent and seasonally flooded areas of Niumi National Park.
The African Rock Python and Royal Python also occur within the Park.
All of these reptiles have been hunted extensively (mainly for their skins) in West Africa and have declined in number (Pauwels and Meirtre, 1996).