The rescue of 12 boys and their soccer coach from a cave in Thailand is not the first time Dr Richard "Harry" Harris has been involved in a harrowing and difficult cave retrieval mission.
The anaesthetist from Adelaide with more than 30 years of diving experience was specifically requested by British divers participating in the Thai rescue.
His cave diving skills were also called upon in 2011, when he had the difficult task of recovering the body of his friend Agnes Milowka, after she ran out of air in Tank Cave near Mount Gambier in South Australia.
Dr Harris was among the expert cave divers who helped police in the recovery of her body, called upon to assist because of the complexities of the almost eight-kilometre stretch of twisting underwater passages.
Ms Milowka, a well-known diver who had worked as a stunt diver on James Cameron's 3D diving film Sanctum, reportedly became disoriented and ran out of air while trying to work out how to get out of a section of the cave.
As with the recovery of his friend's body, Dr Harris has been described as "essential" to a rescue mission to save a young Thai soccer team from their cave prison.
Dr Harris risked his own life on Saturday to make the treacherous journey to the chamber where the boys have been trapped underground for 15 days.
"The doctor from Adelaide has been an essential part of the health assessments for the young boys," Foreign Affairs Minister Julie Bishop told reporters on Monday.
"He is an experienced diver, which is a great benefit because he's brought all that expertise to assist the Thai government in this rescue mission."
It was on his advice the first four boys were cleared to make the incredibly dangerous journey out of the flooded cave complex, emerging alive on Sunday.
One former colleague says there are very good reasons that British caving experts working with Thai authorities at the site asked for his help.
Bill Griggs used to be Dr Harris' boss at South Australia's emergency medical retrieval service, MedSTAR, where the anaesthetist still works.
"To do cave diving, you have to be all about attention to detail and you have to be meticulous," Dr Griggs told ABC radio.
"The combination of his medical knowledge and his cave-diving skills was clearly [why] the British guys requested that he come as well."
Dr Harris is well known in the cave diving community, including as the leader of record-breaking missions to explore a dangerous underwater cave system on New Zealand's South Island.
In 2011 and 2012, he led a team of Australian divers to record depths of 194 and 221 metres in what's believed to be one of the world's deepest cold water caves, searching for the source of the Pearse River.
He filmed the dangerous and complex mission for National Geographic.
It required the team to set up a series of survival pods at intervals to allow divers to decompress, rest and eat in the near-freezing waters along the length of an underwater river - an experience that could prove invaluable in the current rescue mission.
The rescue divers and boys in Thailand must dive, swim and climb their way to safety along a pitch-black tunnel that at certain points is barely big enough to allow an adult to wriggle through.
David Strike has known Dr Harris for more than 10 years and says his unique skill set gives the boys every chance of making it out.
"It's an over-used term, but all of those involved are true heroes," he said.
Fairfax Media and AAP
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