The 46-year-old Australian was with her friend in shallow water at Thornton Beach, Queensland, on Sunday night when she was pulled under.
Her friend attempted to rescue the woman from the reptile’s jaws but was unable to do so.
Searchers scoured the areas in a rescue helicopter fitted with thermal imaging equipment but failed to find any trace of the victim.
Queensland Ambulance Service spokesman Neil Noble said: “The Report that we have from the surviving woman is that they felt a nudge and her partner started to scream and then was dragged into the water.”
Local police Senior Constable Russell Parker told the Australian Broadcasting Corporation: “Her 47-year-old friend tried to grab her and drag her to safety but she just wasn’t able to do that.”
The area where the woman went missing is about 57 miles (90km) north of Cairns and well off the main highway.
Reports varied as to the depth of the water with police saying it was waist deep and paramedics saying she was up to her knees.
The survivor was taken to a nearby hospital in Mossman suffering from shock and a minor injury to her arm.
Reports say the victim was from Lithgow in New South Wales, while her friend was living in Cairns.
Mr Parker said the pair may not have known of the dangers at the beach, which is next to a creek where crocodile-spotting tours happen.
There are warning signs about crocodiles throughout the area.
Warren Enstch, the MP for the area, said the women had to accept some of the blame.
“You can’t legislate against human stupidity,” he said.
“If you go in swimming at 10 o’clock at night, you’re going to get consumed.”
The attack took place near where a five-year-old boy was taken in 2009.
In 1985 a giant crocodile known as Big Jim took local postal worker Beryl Wruck while she was having a late-night swim about an hour’s drive from Thornton Beach.
Crocodile numbers have surged in northern Australia since the animals became a protected species in 1971.