Thai rescue diver shares for the first time how close they came to losing one of the Thai boys.

The entire world was on edge as rescue divers attempted, and succeeded, to save twelve boys and their soccer coach from Tham Luang cave in Thailand earlier this month. But the rescue mission, which was ultimately successful except for the tragic death of one volunteer rescue diver, encountered a few terrifying moments during the rescuing of the final boys and their coach.

As British rescue diver Jason Mallinson held the final boy from inside the cave, already half-sedated in preparation for the three-hour-trip to freedom, he realised that his breathing mask was too small for his face. Without a breathing mask, the child would drown.

“We put it on him, really strapped down tight so his nose was flattened against his face and there was a big gap under his chin. We just couldn’t get it to seal,” Mallinson told ABC’s 20/20.

Without any other options, the brave diver decided to try another mask that also didn’t fit perfectly.

“We knew we didn’t have any more time and we knew this was the last option,” Mallinson said.

“It was so nervous for me because it was the different type of mask with this seal that you could dislodge sideway. I had to be so careful with him,” he continued.

Mallinson’s choice was risky, meaning even the slightest knock could result in the boy drowning. He held the boy’s face close to his body for the whole journey, making sure he hit his own head on any walls instead of the boys.

He added that the advice of Australian anaesthesiologist and fellow rescuer Dr Richard Harris resonated with him as he made the final decision, “No matter what happens, get them out as fast as possible. Hypothermia is going to be a big issue here”.

At the time of the rescue, the young boys, aged 11-16, had been stuck inside the cave for 17 days.

Watch: British diver Jason Mallinson on what happened inside the cave. Post continues after video.

Video via ABC

According to ABC‘s South-East Asia correspondent Liam Cochrane, the narrowest gap in the journey was just 38cm in diameter – only slightly bigger than the width of a school ruler.

The team originally became trapped on June 23.

The head coach of the Moo Pa (Wild Boars) soccer team, Nopparat Khanthavong, had an appointment, so left his 25-year-old assistant, Ekapol Chanthawong, in charge of the team. In a Facebook message shared with The Washington Post, the coach instructed Ekapol, “Make sure you ride your bicycle behind them when you are traveling around, so you can keep a lookout.”

But when the coach checked his phone at 7pm, there were at least 20 missed calls from worried parents, whose sons hadn’t returned home.

He called Ekapol, as well as many other members of the team, and only one 13-year-old answered. The boy told Nopparat that the team had gone exploring in the Tham Luang caves. Nopparat went there immediately – to discover bikes and bags at the entrance to the cave, and water seeping out.

While the boys have now been safely retrieved from the cave, they are still improving physically and mentally.