"I just wanted to get him to the surface as soon as possible," he said.
Ayla-Rā was at the shallow end of the pool when she heard her brother's cries for help.
"I just saw him dragging someone, yelling 'help', so I ran over to him and saw this kid, so I just started holding his head out of the water, while he [Manaaki] ran for help," she said.
Manaaki pulled the boy to the stairs, where Ayla-Rā stayed holding his head above water, waiting for help. A scuba diving group training close by in the pool came to their assistance and began performing CPR.
Neither of the siblings had seen the boy fall into the water but saw that he was bleeding from his head.
"There was so much blood. They used our towels and our towels were drenched," Manaaki said.
The siblings were unsure how the young boy had injured himself.
The boy was "floppy" and not breathing when they pulled him out of the water.
Manaaki and Ayla-Rā's parents were proud of their children's actions, and thankful they had been in the right place at the right time.
"We are proud, and just glad they were there and capable of helping. He was in the deep end, right down the bottom, and not all kids can get down there and pull someone up so for him [Manaaki] to be able to do that, was lucky," dad Rawiri Stewart said.
"If Manaaki had just carried on walking past, he would have been gone."
The injured boy had reportedly gone to the outside pool with a group, but when the group returned to the inside pools, he was left on his own.
Stewart said that when he arrived, the boy was awake and being taken away on a stretcher in the ambulance.
A St John Ambulance spokesperson said the patient was in serious condition when they attended the incident.
Whakatāne District Council general manager community experience Georgina Fletcher said the young swimmer hit his head upon entering the pool.
"He was pulled to the surface by another swimmer and was attended to by staff and patrons on poolside until emergency services arrived."
Fletcher said she, along with the Aquatic Centre staff, were grateful the young swimmer was recovering well and had high praise for those whose actions helped him.
"Council notified Worksafe NZ of the incident, as is standard practice in these situations. Worksafe NZ has confirmed it will not be carrying out an investigation."
Whakatāne Hospital did not respond to queries about the boy's condition at the time of going to press.