A woman who was pulled into crocodile-infested waters in northwestern Australia when a shark bit her finger as she attempted to feed it has described the terrifying moment which nearly cost her a digit.

Melissa Brunning said she was on a yacht in the remote Kimberley region some 2,500 kilometres (1,553 miles) north of Perth when she tried to hand-feed up to four Tawny nurse sharks hanging around the back of the boat.

The two-metre (6.6-foot) creature - which has strong jaws and rows of sharp teeth - sucked at her right index finger "like a Hoover (vacuum cleaner)", she told The West Australian late Saturday.

"I think the shark was in shock as much as I was... the only way I can describe it is this immense pressure and it felt like it was shredding it off the bone," the 34-year-old said.

"I came up and I was like, 'I've lost my finger, my finger's gone'."

Mobile phone footage of the incident at Dugong Bay in late May, aired by commercial broadcaster Channel Seven on Saturday, showed Brunning screaming as she was dragged into the water before the boat's crew and friends quickly pulled her out.