Anaesthetist and expert diver Dr Richard Harris was part of an Australian contingent assisting in the dramatic rescue of the boys from the cave near Chiang Rai in northern Thailand.

After the last boys and the coach were brought out by a chain of divers on Tuesday night, Dr Harris told Prime Minister Malcolm Turnbull via Facetime that the morale of the boys was crucial to their successful rescue.

Dr Harris' key role in the rescue effort involved assessing the boys' health on Saturday and ruling them well enough to be dived out of the cave.

He told Mr Turnbull that the "big heroes" were the children themselves and the Thai Navy SEAL divers who looked after them in the cave.

"They are the toughest blokes and kids I've ever had the privilege to meet," he said.

"They are the ones who were responsible for their own morale and really their own safety and without them being in the state they were in we couldn't have done anything."

After jubilation in Thailand and around the world on Tuesday night following the successful completion of the rescue, Dr Harris learned that his father had died in Adelaide.

Six Australian Federal Police divers, one military, and Dr Harris, supported by a friend from Perth, Craig Challen, were in the rescue effort along with American, British, European and Chinese dive rescue and medical experts.

On Wednesday three of the Australian divers told how the soccer team members were passed "hand to hand" on "sked" stretchers between divers to get them out.

One diver estimated the boys may have passed through 150 pairs of hands in chamber three, after two divers accompanied each of them out of two inner chambers.

The "Wild Boars" team members are recovering in a Chiang Rai hospital.

They were stranded by rising waters 4km into the cave system on June 23, and after being found alive by divers nine days later faced a treacherous journey out through murky water and narrow flooded sections.

The most forbidding part of the journey out of the cave was a U-bend only 30cm wide called "The Choke".

One of the Australian divers said their main job was to move air tanks and other equipment to the end of chamber three where other divers could continue on to extract the boys.

The Australian divers who usually perform "black water", or zero visibility operations, use heavier diving equipment and were limited in their ability to get through smaller spaces.

However, they offered back-up support by checking air tank gauges as they passed and making sure the boys' face masks were properly on.

"For the final three days of the operation we were helping bring the little fellas out. Everyone was given tasks and places to be to assist in handing the young fellas to get them all the way to the front of the cave," one Australian diver said.

Another of the divers said dozens of rescue workers in the cave around 10pm on Tuesday had to flee when pumps holding back water failed, allowing a surge of water just as the last group of Thai navy SEALs was exiting.

He said a roar like a "Mexican wave" echoed along the chamber when the final navy SEAL emerged.

AFP commander Glen McEwen said the biggest challenge for the Australian divers was moving 20 tonnes of industrial-sized pumps, oxygen, medical supplies and food into the labyrinth.

"It's probably the most monumental and inspirational effort they've ever been a part of," he said.

Australian Associated Press