 This crocodile is to be found in the freshwater swamps , marshes and lakes of New Guinea , particularly in the interior . It has been known to enter brackish waters such as those of the Fly River estuary but is very rare in coastal areas , and never found in the presence of the competing saltwater crocodile ( C. porosus ) . The animal was first described from the Sepik River area in the north of Papua New Guinea . A separate population is found in the southern half of the island , with a range that extends from southeastern Papua New Guinea to the Indonesian provinces of Papua and West Papua . It is separated from the northern population by the mountain range that runs along the centre of the island . DNA analysis has revealed these to be genetically separate populations . There are estimated to be between 50 @,@ 000 and 100 @,@ 000 New Guinea crocodiles in the wild . 
