The Duke of Sussex attended all but one of Monday's official engagements without his pregnant wife Meghan after security made the decision not to transport her on the island's bumpy off-road tracks for safety reasons.

Prince Harry's first event for the day was at Pile Valley, where he was greeted by the Butchulla people with a traditional smoking ceremony among the towering satinay trees.

Unveiling a plaque to dedicate the forests of Fraser Island to the Queen's Commonwealth Canopy, Prince Harry said World Heritage sites played a critical role in local economies and livelihoods.

"Their destruction can and is having devastating consequences that go way beyond their exceptional beauty and natural value," Prince Harry said.

"And at a time when so many natural World Heritage sites are under threat, it is more important than ever to protect this island.

"Put simply, without trees and forests we don't surive.

"It is a symbiotic relationship, one that so many people still fail to realise."

The World Heritage-listed Fraser Island, known as K'gari which means "paradise" to the Butchulla people, is the world's largest sand island.

"It is up to us now, to protect this paradise together, not just because it looks beautiful but because it is an essential part of our existence and will continue to be for our children and their children's children."

Aunty Mally Clarke drew laughter from the crowd, of about 70 gathered for the unveiling, when she called out "you're better looking in person".

"I'll take that as a compliment," Harry said.

Prince Harry then saw the crystal clear waters of the island's Lake McKenzie, where he took off his shoes and was cleansed by Aunty Nai Nai Bird, before walking barefoot in the shallows.

Aunty Nai Nai said it would be a day Prince Harry would never forget.

"I think he was blown away ... the size of the timbers we took him to, the beauty of the lakes, you know, talking with our songman, our rangers, and hearing from both points of view on things he had not thought about," she said.

The Duke was whisked through bush to McKenzie Jetty, stopping to shake hands with Butchulla dancers, and land and sea rangers.

In the afternoon, Meghan made a surprise public appearance, meeting adoring royal fans, after joining her husband Harry for a walk along the Kingfisher Bay Jetty.

Meghan, wearing a black and white summer dress by US brand Reformation, and looked relaxed and happy, bent down to speak with several people, including 85-year-old Noeline Walk, who has lived on Fraser Island for 45 years.

Among the crowd were Hervey Bay paramedics Danielle Kellam and Graeme Cooper, who made world headlines after fulfilling a dying patient's wish to see the ocean for the last time.

They handed the royals two teddy bears, dressed as paramedics.

"It was so unreal," Mr Cooper said.

Ms Kellam said the couple were very sincere and genuine.

On Tuesday, Prince Harry and Meghan will leave Australia and travel by charter flight to Fiji's capital Suva, to continue their 16-day tour of Australia, Fiji, Tonga and New Zealand. They return to Sydney on Friday night.

- with AAP, pool copy