"We poked his throat to see if there was anything there and then bubbles came out," George said.
The pair - both Scouts - grabbed the young boy, holding him above the water and tilting his head so he would not choke.
The boys dragged the child to the edge of the pool, where an alerted lifeguard jumped in and pulled him out of the water.
Grant Helleur, YMCA business manager for fitness and recreation, said the lifeguard spoke to the boy on the side of the pool where he started responding.
St John quickly arrived to treat the boy, who was transferred to Starship hospital in a moderate condition.
Despite being proud of his efforts, George said the ordeal scared him.
"My legs shook a bit after and then I didn't go in for a swim for like half-an-hour," he said.
George's mum, Janice, said she was "really, really proud of them both".
She said George was "really freaked" by the incident.
"We live in Beachlands and normally they would go down swimming in the evening but George was like 'I think I've had enough of the water today'."
Mr Helleur also praised the boys for taking action. He said the 5-year-old's mother had also praised the lifeguards and the two boys. It is believed he had had a seizure.
Do you know the 5-year-old boy? Email newsdesk@nzherald.co.nz