Grant Hackett has been found safe and well, police say.

The Olympian was reported missing by his father after he left the Palazzo Versace hotel around 7.30am AEST and failed to make further contact with his family or friends.

"We're extremely worried about him,” his father Nev said this afternoon.

He said when he had spoken with his son several hours ago, Hackett had told him "I love you" before hanging up when asked where he was.

Earlier, Hackett shared a photo of his badly bruised face after his brother spoke out to the media following the Olympian's Gold Coast arrest yesterday.

“My brother comments to the media... but does anyone know he beat the s--- out of me,” Hackett wrote on Instagram this morning.

(Instagram: @grant__hackett)

The photograph appears to show Hackett inside a hospital room, though it is not clear when it was taken.

Hackett was arrested at his parents’ home in Mermaid Waters yesterday after his father was forced to call police when the swimmer reportedly became "aggressive" and "abusive" and began stabbing a chopping block with a knife.

The 36-year-old was taken to the Southport watch house and later released without charge.

He was not sporting the injuries when he was released, and told waiting media that he was “not great”, adding he “probably needed to” seek rehabilitation and medical treatment.

According to the Gold Coast Bulletin, a family member sought a court order against Hackett following an incident that resulted in the Olympian seeking treatment for a facial injury.

The swimmer's brother, Craig, spoke to the media yesterday in an open call for help.

“If there’s anyone out there that can help him, I think we’ve reached the end of the road at this point. Doesn’t mean our love has reached the end of the road, we just don’t know what to do,” he said.

"The Grant Hackett that Australia fell in love with, 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 is there in body but he is not there in mind, soul, or spirit.”

Craig said the family were desperate for “an actual medical diagnosis” and “the right type of treatment” to tackle his mental demons.

Hackett’s father said “alcohol and prescription drugs” are likely the reason for his behaviour.

Regarded as Australia's best 1500m swimmer of all time, Hackett won gold in the long-distance events at the 2000 and 2004 Olympics events and silver at the 2008 Olympics.

He retired from swimming after his near miss at the 2008 Games, and tried and failed to make a comeback by qualifying for the Rio Olympics last year. He was awarded the medal of the Order of Australia in 2001.

The Olympian checked into a rehab facility in the US in 2014 to treat an addiction to the sleeping pill Stillnox and apologised for "poor behaviour" in 2016 after an incident with a passenger on a flight from Adelaide to Melbourne.