Jasmine Lapsley was on holiday in Morfa Nefyn, Gwynedd, when she collapsed after eating a grape in August 2014.
PC Aled Hughes was visiting friends next door and helped give CPR with his wife, a first aid trainer.
The Caernarfon inquest heard Jasmine, from Liverpool, was flown to hospital in Bangor, where she later died.
Giving evidence on the second day of the hearing, PC Hughes described how he found the young girl "motionless".
"Her lips were blue. She was not breathing. She was limp," he said.
He said there was "no sign of life".
Working with his wife Awen, they gave "dozens" of CPR cycles to Jasmine, he told the coroner's court.
He said he was there performing CPR for 10 to 15 minutes, and "it felt like a long time".
He added: "I was very concerned."
His wife told the inquest she was concentrating so hard on trying to save Jasmine, it did not seem like a long time before community first responders arrived.
"I have never seen a child who wasn't breathing before. It was an awful situation," said Mrs Hughes.
But giving evidence, community first responder Rosalind Hemming described the scene as "very confusing".
Community first responders are volunteers trained in life-saving first aid techniques and are dispatched by the Welsh Ambulance Service at the same time as an ambulance crew.
"When we arrived on the scene the patient, Jasmine, seemed to be lying in a whole crowd of people," said Mrs Hemming, who has been a responder for 10 years, and had herself received training from Awen Hughes.
"Awen was ongoing with chest compressions and her husband... mouth-to-mouth resuscitation.
"I asked 'shall we take over?' and she said no."
She later told the coroner that she should have been "more forceful" in taking control of the situation, but at the time she "didn't know my position within the ambulance service".
She also denied an allegation made by Jasmine's family on Monday, that the first responders "shrugged their shoulders" when asked if they had suction equipment.
"We would never do that," said Mrs Hemming.
The inquest continues.
An off-duty policeman spent more than 20 minutes trying to save a choking six-year-old girl while waiting for emergency teams, an inquest has heard.