A New Zealand man and his six-year-old daughter whose disappearance sparked a massive search operation have been found in Australia after a month at sea.

Yachtsman Alan Langdon set sail from Kawhia harbour, on the west side of New Zealand's north island, with daughter Que in a catamaran on December 17.

Langdon says the pair were headed for the Bay of Islands, a short distance away on the other side of the island, but were forced to go off course when a rudder broke and they ran into bad weather.

They turned up 1,616 miles away in Ulladulla, on the south coast of New South Wales, Australia.

"I waited for the fine weather and that didn't come, and at that stage we were getting pushed south and out," Langdon said. "I didn't realise that sailing with one rudder was going to be as difficult."

Que's mother Ariane Wyler, who is estranged from Langdon, hired child-recovery expert Col Champan to help track down her daughter.

Champan told ABC it was the second time he had been hired by Wyler to track down the pair, and said that he suspected they would turn up in Australia.

"The possibility that Mr Langdon has sailed to Australia has always been considered," New Zealand police said in a statement.

It added that the force will now Police will now assess the "background to this matter."