A woman in Australia's Northern Territory forced a prowling salt water crocodile to turn and run after slapping her flip flop against her hand and shouting at the reptile.

The woman was standing with a small dog at the edge of the water at Cahill's Crossing on the East Alligator River in Kakadu National Park when she scared off the crocodile, much to the concern of one onlooker.

"It's just incredible someone would take such a risk. I don't think she realised how dangerous this kind of behaviour is," local crocodile enthusiast Lyndon Anlezark, who filmed the encounter, told Reuters.

Local rangers believe there are more than 120 crocodiles in the six km stretch of river south from Cahill's Crossing.