A fun-loving surfer who died after spending weeks in hospital due to a brutal assault was likely killed by someone he knew, police say.
Guy Haymes, or "Creature" as friends knew him, was found by emergency services in a Manly unit with serious head injuries following a triple zero call about a disturbance in the complex earlier this year.
The 59-year-old was treated at the scene but died in hospital a fortnight later.
Those known to Mr Haymes have been assisting police but there are gaps in the overall story of his death, police say.
After three months of investigations, his family and police are appealing to the public for more information in the hope of finding out who was behind his death.
Brother Mark Haymes said he had been left feeling empty by the mysterious death.
"Guy was fun-loving, sociable and got on with everyone," he told reporters on Thursday.
"With my kids, he was always a really good uncle - they loved him.
"Why someone would actually want to hurt someone as bad as they did ... that's the hardest part to work out."
Mr Haymes lived in Brookvale and might previously have been to the Manly unit where he was found injured.
"It's believed he was there with friends and associates," Detective Superintendent Patrick Sharkey said.
"So it was not unusual that he would have been there."
Not only do police suspect that Mr Haymes knew the person responsible - they believe more than one person could have been involved.
Neighbours, friends and potential relatives of the person involved who might have heard anything about the incident are being urged to contact police.
Police are also appealing for any CCTV or dashcam footage of the Manly area from the evening of February 27.
Mr Haymes was well-known in the Sydney surfing community and beyond.
A paddle-out in his memory at North Avalon is being planned.
