"We do rely on parents to be responsible. It's hard, but some people aren't aware that others don't care."
When staff became aware the three children were unaccompanied, about an hour later, they called their father.
But because it would have taken him an hour to get there, Ms King said she had no option but to call the police.
The children were released back into the care of their father.
It was the second incident these school holidays at Chipmunks in Taupo, which opened in August.
Last week a mother left her 13-year-old son in charge of a younger sibling.
It is illegal to leave children under 14 on their own without taking reasonable steps for their care and supervision.
Businesses such as Chipmunks can accept responsibility for children aged between 5 and 11 but only with parental consent, which requires paperwork to be filed.
Ms King said staff were happy to look after children between 5 and 11 if the paperwork was filed, acting as a babysitter for a specified time.
Rotorua Aquatic Centre has experienced similar cases of children being left alone. In the past staff called police but operations manager Colin Elstob said parents had so far been accepting responsibility these school holidays.
"When I worked on pool deck it used to be really bad - I had to go to court half a dozen times," Mr Elstob said.
"We've had a couple of kids this time but nothing like it used to be. When people come in, the front desk make it really clear what our policy is. It's a nationwide thing.
"We ask for the kids' ages and we're upfront about it.
"When you end up looking after three kids who have been dumped [at the pool] it takes us off from our primary role."
Recently three children were left unattended at the centre.
They were removed from the pool and asked to dress and wait in the reception area to be collected.
"We told them they weren't in the wrong but we can't have one member of staff looking after three kids."
Senior Sergeant Denton Grimes of Rotorua said police had received no reports of children left unattended these school holidays, unlike previous vacation periods.
"I look at kids and wonder where their parents are," he said. "We would probably take some action, a warning or prosecution depending on the circumstances, age of children and how long they had been left."