The boy had been playing on the shoreline when a wave swept him out to sea nearly two weeks ago, but a subsequent air and sea search could not locate him.

A man walking his dog on the beach on Monday afternoon discovered what he believed to be human remains, which were taken for forensic examination, police said.

Inspector Nigel Webber of Brisbane Water Local Area Command said the remains were "partial" and were consistent with that of a child.

"Although we haven’t formally identified the child, our investigations will be surrounding the missing five-year-old," he said. Police expect to identify the deceased within 24 hours.

Chayce's father, Daniel Kelly, earlier said he would not rest until his son had been found. He described him as a cheeky, adventurous boy.

"I just need to find him, I need to get him back," he said.

"I can’t leave him out there; that’s like leaving one of your kids in a different country and not going back to get him but knowing you can never see him again. It’s just wrong. I just want to get him back."

According to resident Anthony Learmonth, Pearl Beach is one of the state's most deceptively dangerous beaches and its waves were breaking violently on the day Chayce went missing.

with Rachel Olding