Grant Hackett's father is pleading with the troubled Olympian to make contact with his family, saying his son is "mentally disturbed" and needs help.
Grant Hackett of Australia catches his breath after competing in the men's 200 metre freestyle during day two of the 2016 Australian Swimming Championships.
The triple Olympian hasn't been seen since this morning and his father Neville is reporting the 36-year-old to police as a missing person.
"He's definitely a missing person and he's mentally disturbed and needs urgent help," Neville said told reporters.
"If anybody's seen him, contact the media or 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 at the Versace Hotel at 7.30am this morning.
Mr Hackett said his son was "very depressed and not in a good condition" when he was last seen.
Hackett's disappearance is the latest twist in a deepening saga that started on Wednesday at midday when police were called to his father's house.
An agitated and verbally aggressive Hackett was calmed by police before being taken to the Southport watch house.
He was released without charge three hours later during which his brother Craig told media about the family's struggles with Hackett's "chronic" mental health issues.
Hackett hit back this morning, posting a picture on Instagram of himself sporting a black eye and cuts to his face.
Hackett accused Craig of assaulting him in what is believed to have been a separate incident last month.
"My brother comments to the media ... but does anyone know he beat the s*** out of me?" he wrote on Instagram.
"Everyone knows he is an angry man."
Fellow Olympian Daniel Kowalski says there had been warning signs about his mental health issues.
The Australian Swimmers' Association boss said he was hopeful Hackett would receive the help he needs to overcome his problems.
"You rely on people talking and seeking help and advice and going to someone, but it's a really taboo subject still," Kowalski told SEN Radio.
"(He needs) some tough love and (to) go to a place that won't let him check out of rehab early.
"Hopefully he can look in the mirror now and say, 'right, its now or never'."