"We chucked him up on that then all three of us waded in," Mr Roberts said.
"When we hit the flats, the fire engine was arriving. I gave him [the boy] my hoodie to keep him warm."
Mr Roberts believed the boy had been out on a tinnie that became beached and had tried to swim ashore.
"We just heard him screaming. You could hear the fear in his voice."
Mr Orr said the fire brigade and police arrived quickly.
All three men spoke of how cold the water was and how bad it must have been for the boy.
St John Western Bay shift manager Kurt Golding said the boy had been on a boat in the harbour with two adult relatives.
The boat broke down and, being low tide, the boy thought it would be shallow enough to walk to shore.
"There were a couple of deep parts and although the boy didn't have any trouble swimming, he got too cold.
"He called for help and luckily enough, there were some guys nearby able to help."
Mr Golding said the youngster had been taken to hospital suffering from mild hypothermia.
"He was frightened, shaken up and obviously pretty cold, shivering away. After 10 to 15 minutes in the truck with the heaters on, he was a lot happier."