Crystal Beale went to dinner with family. She never made it home.

On a Friday night almost three weeks ago, Crystal Beale went to dinner with family and an ex-partner in Brisbane. She spent the night catching up with loved ones.

They never saw her again.

Hours later, a member of the public discovered her body in the Brisbane River.

No one knows how or why the mother-of-two ended up there. But detectives say they are determined to find out, as they work around the clock to piece together her final hours.

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Police are retracing what they know of Crystal's final steps. At this stage, more questions than answers remain.

"She was visiting family, and we believe where she's left, she left a man known to her, and that's where she's gone missing. And that's what we're trying to piece together, her movements after that," Detective Acting Inspector Rod Watts said.

On February 21, sometime before 9.30pm, Crystal was seen leaving the Sunnybank Hotel wearing a long white dress, brown slides and a brown cross-body bag.

CCTV footage shows her pause to put on one of her shoes, as she walks behind two men.

Police said she was dropped off in West End in Brisbane's inner south where her family lives.

Police have released CCTV of Crystal on the last night she was seen alive. Image: Queensland Police.

Between the hours of 9.30pm and 1am, Crystal was seen on Ryan Street in West End and near the Orleigh Park sailing club on the Brisbane River.

About 5:40am on Saturday, a rower made the tragic discovery of her body in the river at Yeronga.

Initially, Crystal showed no obvious signs of injuries, prompting her death to be ruled non-suspicious. However, a homicide investigation has since been launched following further investigations and a post-mortem.

Police believe Crystal had been in the water for about six hours.

"A post-mortem has not determined a cause of death, but we don't believe she has died under natural circumstances," Watts said.

"The injuries that have been uncovered in the postmortem suggest to us her death is suspicious."

There was no suggestion a weapon was used, he added.

Watts said Crystal was with a former partner before she went missing.

There was an expired domestic violence order against her former partner but nothing current, he said.

He's not accused of any wrongdoing and has not been charged. No one has been taken into custody.

Police have not ruled out whether it was a random attack.

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'She was my everything.'

"Crystal was a much-loved mother and friend," Watts said. "Her death in these circumstances is horrific and we are seeking justice for her and her family.

"To go missing in these circumstances and for three weeks trying to piece it together ... at this point of time, we're still seeking answers. They want answers."

Crystal leaves behind two children, aged 22 and 15, who police said were "struggling" with their mother's traumatic death.

Her daughter Charlie-Rose Wagner told Brisbane Times there were "no words to describe how painful this is".

"Myself and my family just want answers," she said. "My mum was the most beautiful woman I've ever known. She was my everything."

Crystal's family are calling for answers. Image: Facebook/crystalbeale.

Friend Deborah Makim described Crystal as "such a gentle soul".

"So caring and loving, so devoted to her two beautiful children," she told 7NEWS. "I would just like her not to go unremembered."

Police are urging anyone who might have been in the Orleigh Park area between 9.30pm on February 21 and 1am the following morning, or who might have seen Crystal or any suspicious behaviour, to come forward.

Mamamia has contacted Crystal's family for comment.

Feature image: Facebook/crystalbeale.