Missing yachtie Alan Langdon and his daughter Que Langdon have been found alive in Australia, a child recovery expert claims.

Langdon, 49, and his 6-year-old daughter set sail from Kawhia Harbour in the Waikato on board a 6.1 metre Wharram catamaran on December 17, and had not been seen or heard from since.

The pair were found in Ulladulla New south Wales, says New Zealand Police. However, Australian authorities are yet to officially confirm their identities.

Police were notified earlier this afternoon by Australian authorities after the pair arrived into Ulladulla on Langdon's catamaran. Police understand the pair are both well, and Langdon is currently talking to Australian officials.

They are currently liaising with its counterparts in Australia and awaiting further information about Mr Langdon's journey.

The girl's mother has been notified.

Following their disappearance, an extensive search was conducted of sea and coastal areas between Wellington, Cape Reinga and the Bay of Islands.

The possibility Langdon had sailed to Australia had always been considered.

Child recovery expert Col Chapman, who'd been hired by the girl's mother Ariane Wyler, says he was informed through a leak from official sources the pair have been found alive in Australia, reports Fairfax.

"We got them. Just landed in Australia," he said via text.

It's also reported a member of the public tipped Child Recovery Australia off after seeing a poster of the pair which the organisation had distributed.

Australian authorities were alerted to the chance Langdon and his daughter may have made landfall in Australia.

Waikato police Detective Sergeant Bill Crowe confirms Interpol alerted Australian authorities as part of the investigation into the missing pair.