The 47-year-old Brisbane mother who went missing from a cruise ship off New Caledonia deliberately fell from the ship, police say.

The Highgate Hill woman, named on social media as Natasha Schofield, was talking with her husband on the deck before she took two steps back and propelled herself overboard.

Police Inspector Rob Graham said the husband attempted to grab onto her legs but was unable to save her. He immediately raised the alarm.

The mother of three children, aged between 12 and 16, is presumed dead though her body has not been recovered. Her two daughters and one son were on board but are not believed to have witnessed their mother fall.

Inspector Graham confirmed the nature of the tragedy after reviewing CCTV of the incident: “This wasn’t an accident.”

“What I saw was a couple of loving people on the top deck of a cruise ship,” he said.

“I saw them leaning on the rails and I saw the intentional actions of the missing person take two steps back and then propel herself over the railing.

“I can also say that her husband tried in vain to grab her as she went over, by grabbing onto her legs, but she was too far gone.”

Inspector Graham said it was important to be “open and honest about mental health”.

“It’s a tragic end to what should’ve been a lifetime holiday experience for a loving family.”

Earlier reports she had been sick or fell due to a freak wave were incorrect, Inspector Graham said.

The Pacific Dawn cruise ship was about 150 nautical miles west of New Caledonia at the time of the incident, about 5pm local time on Thursday (4pm Brisbane time).

The search was called off by Friday morning following advice from marine rescue experts.

Passengers disembarked at Brisbane on Sunday morning.

Inspector Graham praised Ms Schofield’s husband for not going in after her and endangering himself.

“We’re just lucky that there’s not two people missing.”

The cruise operator, Carnival Australia, handled the incident with unquestionable professionalism, he said.

“We will be able to give police CCTV footage providing an unobstructed view of what happened and portraying an obviously devoted and loving couple,” Carnival said in a statement.

“We extend our deepest condolences to the family and hope that they will find comfort in their grief.”

Police are preparing a report for the coroner.

Counselling was available for passengers and crew.

Readers seeking support should contact Lifeline on 13 11 14.

-with AAP