As celebrations rang out across the world over the stranger-than-fiction Thai cave rescue's success, a hero who was the last to leave the mountain found out his father had died.

Adelaide anaesthetist and underwater cave explorer Richard Harris — known as Harry — is understood to have been the last person to leave the cave overnight, having played a crucial role in the complex mission to save the young boys and their coach.

The 53-year-old gave up a family holiday and made his way to Northern Thailand, where he scuba dived 4km through cold, dark and narrow passages to reach the boys and assessed them as medically fit to attempt the risky escape mission.

And, this afternoon it has been revealed that his father died overnight, just a short time after he completed the rescue mission.

In a statement his colleague, MedSTAR Director of Clinical Services Dr Andrew Pearce said it was "with great sadness Harry's dad passed away last night".

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Dr. Richard Harris (right) and his dive partner Craig Challen, taken after they completed the mission. Photo / Australian Ministry for Foreign Affairs

"All the team at SA Ambulance Service is incredibly proud of Dr Harris," the statement read.

"It has been a tumultuous week with highs and lows. We are delighted that Harry and the boys are safe and that he was able to play such a remarkable role in the Australian response.

"Harry is a quiet and kind man who did not think twice about offering his support on this mission.

"It is with great sadness that I confirm that Harry's dad passed away last night a short time after the successful rescue operation in Thailand.

"I have spoken with Harry. This is clearly a time of grief for the Harris family, magnified by the physical and emotional demands of being part of this week's highly complex and ultimately successful rescue operation."

Harris was one of the 19 divers who helped escort the final five members of the group out of Tham Luang cave, in the toughest rescue operation of the past few days.

Using his 30 years of experience, the South Australian assessed which of them should be saved first and checked up on their physical conditions as they were escorted through the cave's perilous network to safety.

The team of doctors Dr. Harris worked with plus 2 DFAT officers taken after they completed the mission. (Photo / Australian Ministry for Foreign Affairs)

Now there are calls from hundreds of Australians on social media for the expert medic and cave diver to be handed the Australian of the Year award for his heroics in the incredible rescue mission.

"If ever a bloke deserved to be Australian of the Year it's this man," wrote one commenter on Twitter. "He's what embodies the true spirit of this country."

"Words can't even describe how proud this guy makes me feel to be Australian," wrote another. "In a world where we sometimes honour people for the most meaningless reasons, surely it's time we recognised a real-life hero like Richard Harris."

British divers specifically requested the talented medic for the rescue operation which claimed a life of one of the cave divers taking part.

However, it is not the first time Dr Harris has found himself at the centre of a tragic rescue operation.

The well-known diver was also summoned for an extremely difficult and life-threatening cave diving mission in 2011, when he was tasked with recovering the body of his mate Agnes Milowka.

She ran out of air during an expedition at Tank Cave near Mount Gambier in South Australia, but Dr Harris had to find the strength to pull his mask on and recover her lifeless body from the dangerous cave.

This is Dr Richard Harris. The Australian anesthesiologist, aeromedical consultant, cave diving expert with over 30 years experience. Responsible for co-ordinating the #ThaiCaveResue operation.

When your children ask about heroes, tell them about him.#ThailandCaveRescue pic.twitter.com/hRnycGqHzB

— Rahul Setia (@rahulsetia007) July 10, 2018

South Australian police specifically requested Dr Harris because of the complexities of the almost 8km stretch of winding underwater passages inside the perilous cave network.

She is understood to have become disoriented during the tragic 2011 mission in South Australia and ran out of air while trying to work out how to navigate a difficult section of the cave.

The heartbreaking mission is just one of many over Dr Harris' illustrious career, which have propelled him to become one of the most sought-after professionals in the field.

He's been described as "essential" to the rescue bid to save the trapped Thai schoolboys because of his unique skills and experience.

"He's an interesting character," MedSTAR clinical director Andrew Pearce told reporters on Monday as the rescue efforts in Thailand continued.

"Harry is selfless. He is extremely thoughtful. He's a quiet person. He is the type of guy who will give of his all.

"He was actually meant to be on holiday and gave up his holiday so that he could be part of this."

Chiang Rai governor Narongsak Osottanakorn also praised Dr Harris' efforts overnight.

"(The Australians) have been a big help, especially the doctor," Mr Osotanakorn told9 News. "Very good. The best — not good — the very best."

Aussie doctor Richard Harris has been in the cave with the boys three days in a row. He gives medical sign off before each boy swims and dives out only leaves the cave AFTER the day’s operation has been completed. Just, wow. #thaicave #thaicaverescue #thamluang

— James Massola (@jamesmassola) July 10, 2018