A one-punch attacker has been sentenced to five years in jail for fatally assaulting a former star surfer.

Grant Alec Coleman, 43, killed former pro-surfer Chris Davidson, 45, in a one-punch assault outside the South West Rocks Country Club on September 24, 2022. 

Newcastle District Court heard Mr Davidson was a convicted child sex offender and Coleman told police he was "triggered" after he saw him with a young woman.

Judge Peter McGrath noted Coleman had yelled out "paedophile" to Mr Davidson several times both inside and outside the club on the night.

Judge McGrath said Mr Coleman had an intense dislike of Mr Davidson and "developed a fixation on him".

"Mr Coleman felt justified in taking the law in his own hands ... in Mr Coleman's point of view, he was like some unofficial sheriff of South West Rocks.

"He was the judge and jury of Mr Davidson."

Mr Davidson famously beat surfing legend Kelly Slater in two consecutive heats at Bells Beach in 1996.

Coleman pleaded guilty in August last year to charges of assault causing death and common assault.

When he took the stand during his sentencing hearing, Coleman said he "wanted to protect young girls".

He said the night of the assault had "haunted" him.

"I realised what I'd done. I wanted him to wake up, to regain consciousness," Coleman said.

Mr Davidson's sister was angry and emotional when she read her victim impact statement in response to Coleman's claims.

"He spent all of his life surfing and he was never attacked by a shark but he was taken by a human shark," she said.

Coleman will be eligible for parole in September next year due to time already served.