South Australian anaesthetist Richard Harris and West Australian retired vet Craig Challen were given the award for their role in the daring rescue of 12 young boys and their coach from a flooded cave in Thailand.

The veteran cave divers played a crucial role in the international rescue operation, drawing worldwide praise and admiration for their part in the dramatic mission.

The close mates stood together on stage at the National Arboretum on Friday, accepting the award after Prime Minister Scott Morrison revealed they had won.

Dr Harris said the pair's actions showed why it was important to let children explore the world.

"Anyone with a measure of enthusiasm can achieve the sort of things that we've done," he said.

"I can't bear to see kids squander any of these opportunities, trapped indoors, eyes glued to a screen."

He's planning to spend 2019 encouraging Australia's youth to find their "inner explorer".

"Equally importantly to ask parents to relax a little and let them have a bit of rope to do that," Dr Harris said.

"Outdoor activities really do promote physical and mental wellbeing and it's critical that kids can test their own limits."

Mr Challen said he was astounded the pursuit of a hobby for more than two decades led to worldwide recognition and Australia's top award.

He wants to use his platform to encourage all Australians to get the most out of life.

"I urge all Australians to make the most of every opportunity that presents itself and in every decision you make, ask yourself, does this help me to be the best person that I can be?" Mr Challen said.

"Thank you for this great honour. I feel flattered and privileged to be numbered amongst an extraordinary group of people, both previous recipients and this year's nominees."

After their speeches, a video message from the Thai soccer team they saved was played on the big screen.

"We love you, all the best," the boys said.

The two men teared up, with Dr Harris revealing it was the first time they had communicated with the boys.

Mr Challen said the bottom line was there are 13 families that have still got their sons, which wouldn't have been the case without the rescue effort.

"That's what floats my boat," he said.

Earlier Mr Morrison addressed the ceremony where he paid tribute to nominees across all categories.

"You, our nominees, are our best, having made our nation kinder, smarter and more accepting," the prime minister said.

"You've made Australia even stronger and I want to congratulate you."

Australian Associated Press