Police said a 36-year-old man reported missing on the Gold Coast earlier on Thursday had been found safe and well.

EARLIER

Grant Hackett's family has reported the Olympic champion missing and appealed for the public to help find him.

Neville Hackett, the father of the troubled swimming champion, told media on Thursday he hadn't spoken to his son for several hours.

"He just hung up when we asked him where he was," he told reporters.

"He's definitely a missing person and he's mentally disturbed and needs urgent help.

"I would think if anyone has seen him, to contact the media, the police or the Hackett family.

"Grant, let us know where you are, we love you and we want to help you."

Hackett was last seen leaving the Palazzo Versace hotel on the Gold Coast's Main Beach about 7.30am on Thursday morning.

Mr Hackett said his son was "very depressed and not in a good condition" when he was last seen.

"His doctor can't find him, he hasn't kept an appointment with his lawyer," he said.

"We believe at best he is probably in a hotel somewhere on the Gold Coast, that would be the best scenario we could imagine.

"We are extremely worried about him."

The Olympian was arrested on the Gold Coast on Wednesday afternoon after a disturbance at his parents' Mermaid Waters home, where he allegedly became agitated and verbally aggressive.

He was later released without charge.

Brother Craig spoke to reporters outside the family home on Wednesday, saying the family didn't know how to deal with his erratic behaviour.

"The whole family have done everything that we can but now it's kind of out of our hands, it really is," Craig said outside their home.

"This is not Grant Hackett. This is a completely different person. I don't know this person; my mum and dad don't know this person," he said.

"He's there in body but he's not there in mind, soul or spirit.

"From a mental health perspective, I hope something can be done."

On Friday morning, Hackett lashed out at Craig in a post on his Instagram page.

"My brother comments to the media ... but does anyone know he beat the shit out of me," he wrote.

"Everyone knows he is an angry man."

Queensland police said Hackett had not yet been formally listed as a missing person.

Hackett was reportedly treated in hospital overnight after his doctor picked him up from the Southport watchhouse.

He told reporters after his release he was not feeling great and would be seeking help.

The three-time Olympic gold medallist has struggled with addiction and other personal issues since his retirement after the 2008 Beijing Games.

People who need support can contact Lifeline on 13 11 14.

With AAP