A woman who witnessed a crocodile mauling her close friend on a northern Australian beach has recounted the horrifying moment the creature struck.

Leann Mitchell was with Cindy Waldron on the night of May, 2016, when the giant reptile snuck up on the two women as they frolicked at Thornton Beach, 130km north of Cairns.

They were there to celebrate the end of Ms Mitchell's breast cancer treatment, and were standing in shallow water, arm-in-arm, Sunday Night reported.

Leann Mitchell (pictured: right) witnessed her close friend Cindy Waldron (pictured: left) being mauled by a killer crocodile

The two women were frolicking at Thornton Beach, 130km north of Cairns, when the creature struck

It was a dark night and her friend's back was to the water, Ms Mitchell recalls.

The two women were laughing.

'And then Cindy cried out to me and she said "It's got me" - I thought it was just that fright you get when seaweed brushes you.'

Leann Mitchell, above, was celebrating beating breast cancer in Thornton Beach, Cairns when the crocodile crept up on the pair

Ms Mitchell has recounted the horrifying moment the crocodile yanked her and her friend into the water, saying that she felt the top of its head and started trying to punch the creature

Ms Mitchell suggested that she didn't fully understand what was happening until the moment both women were yanked into the water by the powerful animal.

She recalls the moment she reached out and felt the top of the creature's head; the moment she started punching and hitting the crocodile as it yanked them a second time; and, finally, the moment Ms Waldron disappeared.

'The only help I could get was by screaming Cindy's name,' Ms Mitchell said.

A few weeks later, the 4.3 metre crocodile that is thought to have killed Ms Waldron was captured by wildlife officers in the Daintree. Police found human remains, believed to be those of Ms Waldron, inside the animal

Leann Mitchell (above) was celebrating beating breast cancer in Thornton Beach, Cairns when the crocodile crept up on her and her friend, Cindy Waldron, on May, 2016

Speaking to the Cairns Post the next day, a local man confirmed that crocodiles are 'clearly in the area.

'They're semi-nocturnal: definitely in the evenings they come out, when it's warmer. And they hunt.'

A few weeks later, the 4.3 metre crocodile that is thought to have killed Ms Waldron was captured by wildlife officers in the Daintree, and subsequently euthanised.

Police found human remains, believed to be those of Ms Waldron, inside the animal.