The unexplained death of a teenager whose chain-bound body was pulled from the Murray River 30 years ago is being reviewed by police, following a social media campaign by his family.

The badly decomposed body of Robby-Jo Coulter, 17, was discovered by campers between Trentham Cliffs and Monak, just south of Gol Gol in far-south-west New South Wales on January 3, 1989.

His body had been weighed down with 21 kilograms of chains and mill bricks, his hands bound with chains behind his back and secured with bolts.

Key points: Robby-Jo Coulter's body was pulled from the river bound by chains and weighed down by bricks

Robby-Jo Coulter's body was pulled from the river bound by chains and weighed down by bricks His family believe someone must have information about his death

His family believe someone must have information about his death The NSW deputy coroner at the time said he was "quite satisfied" Robby-Jo had not been murdered

The teenager was last seen walking from a New Year's party along the side of the road in the early hours of New Year's Day.

'Quite satisfied' teen not murdered: coroner

The then NSW deputy coroner Derrick Hand said he was "quite satisfied" the teen had not been murdered.

But 30 years on, his family are still searching for answers.

Robby-Jo Coulter's family are seeking closure and say someone must have information about his death. ( Suppled: Tiffiny Coulter )

"Thirty years ago today, on New Year's Eve, my older brother's life was taken. He was 17 years old. It was brutal. It was violent," Robby-Jo's sister Tiffiny Coulter wrote on social media.

"I can't possibly imagine the fear that filled his soul as he sank to the bottom of the Murray River with 21kg of brick and chain wrapped around his body.

"The case remains unsolved. We have no idea what happened. Thirty years, and we still have no closure," she wrote.

'Someone knows something'

Speaking with ABC Radio Melbourne, Robby-Jo's mother Suzie Coulter said someone knows something.

"I'm convinced that all his mates know what happened. I don't know why they're staying so silent," Ms Coulter said.

"I don't know what really happened. All I know is that my family needs closure and we've waited 30 years for that," she said.

Ms Coulter said every New Year brought the memories flooding back.

"I tried hard to come to terms with it, I've tried to move on and so have the girls but every year it comes back at you and there's no escaping from that," she said.

"And while there's no answers, we'll be asking every year."

Police would not say what triggered the review but a spokesperson said the investigation remained the responsibility of the Homicide Squad's Unsolved Homicide Unit.

"This case will undergo a formal review under the unit's new processes in due course," the spokesperson said.