Divers successfully rescue four boys but have to leave the remaining eight and their coach behind for now due to low oxygen tank supplies.
Two New Zealand divers have weighed in on the rescue of 12 young footballers and their coach from a Thai cave, calling it "a massive ordeal" and "unbelievably stressful".
Professor Simon Mitchell, head of Anaesthesiology at Auckland University and a professional diver, spoke on Newstalk ZB this afternoon and said Thai authorities had constructed the best rescue plan from a number of very bad options.
"I think it is very well constructed and I think the Thai authorities have done exactly the right thing.
"They have brought in a large team of people with true expertise in cave diving and they are not relying on their own local navy people – they have gone around the world to get the team that they needed," he said.
Thai rescue teams arrange water pumping system at the entrance to a flooded cave complex where 12 boys and their soccer coach have been trapped since June 23. Photo / Royal Thai Navy
Mitchell, a lifelong passionate diver, knows some of the crew responsible for getting the children to safety after they have spent 15 days underground.
"I haven't spoken to Richard Harris - who is anaesthetic colleague of mine and an expert cave diver from Adelaide – but he is the one who is in the cavern with the boys at the moment.
"My understanding is, he is responsible for triaging the kids."
Mitchell believes some of the strongest children would have been the first rescued after four of the boys were brought to safety this morning.
"My sense was, they would at least for the first couple, send out the strongest kids to test the protocol to give it the best chance of success but just like you I am hearing these conflicting reports and I really don't know what to make of it."
He said the dive itself was not physiologically challenging, but the main challenge was supporting the children who have never dived, don't swim and are not water-confident.
"They are being asked to close their eyes, breathe from an unfamiliar device and essentially be guided through these narrow, terrifying tunnels that are putting them in a lot of danger.
"The key is to try and stop them from panicking."
He said rescuers will have spent the past few days preparing the children for the dive and familiarising them with the equipment.
"They will have spent a lot of time immersed in the water in the cavern where they have been staying, just trying to get used to breathing underwater and getting used to this idea that they are going to have to entrust themselves to someone to guide them through this labyrinth."
Neil Bennett, director of New Zealand Diving, said one of the biggest risks for the boys being rescued is that they will panic and pull off their breathing masks.
He said very few people could cope with the demands of cave-diving, which was for elite divers, not the untrained.
"What's being asked of them is a massive ordeal."
Bennett said that commonly when someone panicked while diving they automatically spat out the regulator and bolted for the surface for air - but in some places in the Thai cave the water was flowing hard up to the ceiling so there was no air to breathe.
A different kind of risk came from holding one's breath while ascending near the surface. Because of the rapid pressure changes in this zone, the lungs could be damaged.
He said other risks included getting lost in the muddy water, banging into the rocky walls, floor and ceiling, and lung damage.
In the narrower areas there was a risk of hitting rocky outcrops which could cause lacerations or concussion.
However, Mitchell said the natural confidence of boys might work in the rescuers' favour.
"Children are quite positive about these sorts of things because they are naturally adventurous. It might have been harder with a whole lot of adults."
Bennett said there were also major risks associated with staying in the cave.
The oxygen level in the confined space's air was down to 15 per cent, from a normal level of 21 per cent.
"It's at the level that it causes problems. The increase in carbon dioxide levels leads to judgement problems, concentration problems, severe headaches."
He said a tactile guideline had been placed for the rescuers and boys to follow by holding on to it.
Bennett doubted that the boys and their rescuers would be tied to each other in the way that alpine guides and their clients are often attached by harnesses and a rope.
He expected the rescuers and the boys would communicate underwater by a system of touch or squeeze-based signals.
Once rescued, Mitchell said the children may be suffering from skin and air infections but the biggest concern would be post-traumatic stress.
"One of the things that is not being talked about too much given they have been found and the rescue is under way, is that these children have been through an extraordinarily stressful period before they were found – nine days underground, in the dark, with no sense that they are definitely going to be rescued.
"That must have been unbelievably stressful and I suspect there is going to be a lot of getting over that."
