The unnamed tourist is said to have yelled “a croc’s got me” before she disappeared below the surface.
The 46-year-old was swimming with her friend in shallow waters in a national park in Queensland, Australia.
But tragedy struck when the pair, who went for a dip around 10.30pm in the World Heritage listed Daintree Park, caught the attention of the predators.
Police Constable Russell Parker said: "Her 47-year-old friend tried to grab her and drag her to safety but she just wasn't able to do that."
Neither of the women were from the local area, he added, which meant they may not have realised they were splashing around in a crocodile habitat.
It is thought the victim was from New South Wales, Australia.
Related articles
The second woman was treated for shock and taken to hospital, but managed to raise the alarm.
After the alarm was raised, helicopter was drafted in to help with the search.
Despite using its thermal imaging camera, they were unable to locate the the woman’s body.
So far search operations have been unsuccessful, but will continue.
But Warren Entsch, who represent the area in Australia’s parliament, criticised the pair for swimming in the crocodile-infested waters.
Crocodile crushing turtle
He said: "You can't legislate against human stupidity.
"If you go in swimming at 10 o'clock at night, you're going to get consumed."