A man has been charged with the murder of a well-known surfer who was allegedly attacked at a unit in Sydney's northern beaches.

Guy Haymes, 59, who was known as 'Creature' to his friends, was found with serious head injuries inside a unit on Pittwater Road in Manly on February 27 of this year.

Police allege Mr Haymes had been assaulted inside the apartment, which was not his residence.

He was rushed to Royal North Shore Hospital but died 15 days later.

Police established Strike Force Flat to investigate his "suspicious death".

A 41-year-old man was arrested in Greenacre in Sydney's west on Saturday night.

He was taken to Bankstown Police Station and charged with murder, two counts take/detain person with intent to obtain advantage and take/detain person with intent to obtain advantage occasion actual bodily harm.

The man has been refused bail and is expected appear in court today.

On Thursday, police held a press conference appealing for witnesses and people with information about the "serious assault" to come forward.

Mark Haymes also spoke at the press conference, where he described his brother as "fun-loving," "sociable" and "kind-hearted".

"He was very warm, and welcomed people into the community with open arms," he said.

"Our whole family is in shock and disbelief that he had his life cut short, and in such a brutal way. Not knowing what happened that day and not having the answers is the hardest part."

Police suspect Mr Haymes knew who assaulted him.

Mr Haymes was a high-profile surfer who was well-known in the northern beaches community.

He participated in surfing competitions including the Rip Curl Shield in the 1980s.