Princess Mary and Crown Prince Frederik were enjoying a rare outing when their eldest boy Prince Christian was swept off-shore by a rip at Mermaid Beach.
It was only the quick action of Kiwi lifeguard Nick Malcolm that saved the life of the future king.
Witnesses told how Nick paddled out and brought the 10-year-old prince back to safety, much to the relief of a terrified Mary and Frederik who were watching on from the beach.
Christian had been playing between the flags at the time, while his parents were in the shallows, witnesses report.
Nick spotted the young boy in trouble, paddled his board out to him and plucked him from the water.
“We got him before it got too serious, but he wouldn’t have come back in,” says Nick’s supervisor Stuart Keay.
Laid-back Nick had no idea who he was rescuing at the time and has taken it all in his stride, keeping a low-profile since making worldwide headlines.
“He’s kept it pretty quite,” confirms fellow lifeguard Shane Pierce.
“We’ll give him plenty of stick now we know.”
Shaken but not deterred by the scare, Princess Mary, 43, and her family returned to the beach the next day, keeping well between the flags and staying closer than ever to the shore.
They’re making the most of their first festive holiday in Australia since 2011.
They arrived in Perth on December 6 to visit Mary’s Perth-based brother John Donaldson, who is the godfather to Prince Vincent, four, in a low-key visit before the Gold Coast drama.
The family spent some time at Dreamworld theme park earlier in the same week and the princess also managed to do some shopping with her daughters Princesses Josephine and Isabella at Marina Mirage shopping centre.
The royals are heading to Mary’s home town of Hobart in Tasmania for Christmas.
Meanwhile, for handy first-aid tips this summer click here.