Now, for that bravery on the broken raft at the Dreamworld theme park in Queensland, the Canberran is to be honoured with a posthumous award.

"I'm very proud of him," Luke's mother Kim said about the Commendation for Brave Conduct award. "I'm overwhelmed that the nation has decided to celebrate something that Luke did."

Luke was one of six people in a raft on the Thunder River Rapids Ride at the theme park on October 25, 2016 when there was a malfunction in the pumping system and rafts clashed.

Moments before his raft flipped over, he leaned across and stopped his 12-year-old niece Ebony tipping out. She managed to escape but he was tipped into the water to die seconds later in the ride's mechanism.

His partner Roozi Araghi also died, along with Luke's sister Kate Goodchild. Cindy Low from Sydney was the fourth victim.

The mother of Luke and Kate said the award for her son's heroism was "bitter sweet".

"I think it says a lot about the person that Luke was, that he did what he did - but it's very sad that he died in the accident itself," Kim said.

"My Kate was the first in the water and then Luke went in so we are not talking a long time but that was probably the longest seven seconds in Luke's life."

Thursday would be Luke's 43^rd birthday. "It's the first time there's been a little bit of brightness around Luke's birthday since the accident," his mother said.

As for the award, "Luke would be absolutely chuffed but he wouldn't have liked the fuss around it. He would be proud and humble as well."

Luke was the uncle who spoiled the niece whose life he ended up saving. "Luke spoilt her rotten. He would say, 'If she wants it, I'll get it. If she needs it, her mother can get it'."

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The theme park Dreamworld's parent company was fined $3.6 million in 2020 for its negligence.

A Workplace Health and Safety prosecutor told the court that while the pump failure was the direct cause of the accident, there was a list of previous failures.

Earlier safety audits had shown that a special water level sensor could have prevented the accident. It would have cost less than $3000.

The pump failure was the third that day and the fifth in a week, but no automated shutdown device had been installed despite recommendations.

At the court, Kim Dorsett said that she cried "for my lost children every day".

She said she would always be haunted by the words of Ebony, her granddaughter whose mother had died.

"'I could not find mummy' - these words have become recurring nightmare words that will stay with me until my dying breath," she said.

She said that every day she woke and then remembered her great sadness.

"I have to have another day in this hell. A broken heart has no words," she said.