Police were called to the scene at 11.02am.
A St John spokesperson said a crew responded with one ambulance, one manager and two rapid response vehicles at 10.59am.
Next Gen gym has been approached for comment.
This is the latest in a spate of indoor pool-related incidents in the last month.
Two men were found motionless at the Newmarket Olympic Pools and Fitness Centre on Saturday. The pair were taken to hospital in critical condition.
A representative for the family of one of the men said they were “swimming to touch the bottom of the pool”.
They were pulled from the water by champion swimmer Joel Crampton.
A member of the public also saved a young boy’s life at the nearby Albert Aquatic Centre when he was found unconscious at the bottom of a pool.
Witnesses said lifeguards were distracted and “slow to act” - even after the boy’s panicked mother raised the alarm.
One woman said one lifeguard was on his phone and wearing headphones and another two were talking.
The boy’s father said he had been told it was lifeguards who pulled his son from the water and resuscitated him.
“We never knew of the hero person who found him under the water and the hero doctor,” he said.
Rachel Maher is an Auckland-based reporter who covers breaking news. She has worked for the Herald since 2022.