A New South Wales woman travelling in the Northern Territory accidentally submerged her four-wheel-drive in a crocodile-infested river after mistaking a boat ramp for a river crossing.

Photographs released by police show a crocodile lurking close to where the woman's white Troop Carrier became stranded in the East Alligator River, about 300 kilometres east of Darwin.

Police said the woman had mistaken a boat ramp for Cahill's Crossing, where vehicles are able to cross the river between Kakadu and Arnhem Land.

In 1987, a 40-year-old man was decapitated by a five metre crocodile near the area where the woman's car became submerged.

Two people, including a 11-year-old girl, have been killed by crocodiles in the Territory this year.

Police say the woman was able to get out of her vehicle and back to the riverbank without any problems from crocodiles.

But they have reminded tourists to take extreme care near Top End waterways.

"Members of the public need to be reminded that when travelling through the NT it is their responsibility to research the area and be aware of the extreme road conditions, especially that of remote areas," Brevet Sergeant Ben Higgins said.

"All water crossings should be considered extremely dangerous and exceptional care should be taken to avoid similar incidents such as these, especially considering the number and size of crocodiles that inhabit remote waterways."