Missing yachtie Alan Langdon is likely to be sailing his tiny catamaran to Australia, where he has disappeared with his 6-year-old daughter Que previously, according to a top child recovery expert enlisted to find them.
Experienced seaman Langdon, 49, and his daughter left Waikato's Kawhia Harbour bound for the Bay of Islands on December 17 and have not been seen or heard from since.
Border alerts are in place and Interpol is working with New Zealand police, while Langdon's bank accounts and phone records are also being checked as the search for the missing pair ramps up.
The official search is now concentrated in the Northland area after police received sightings of a vessel similar to Langdon's heading in that direction over the past few days.
The girl's mother, Ariane Wyler, told the Herald that she separated from Langdon last year.
Wyler - who lives at Golden Bay in the South Island but is on holiday in her native Switzerland - has now hired Australian child recovery specialist Col Chapman to help find her daughter who she has not seen for 20 months.
"I am deeply distressed about this current situation and miss my daughter Que greatly," she said.
"I am strongly convinced that they both are alive, well and safe. I believe in Alan Langdon and his capabilities as a seagoing person. My gut feeling tells me that they are further offshore to the west."
She described Que as a "beautiful daughter" and a "gorgeous little person".
Chapman will arrive in New Zealand either Sunday or Monday to begin his inquiries.
However, he told the Herald today that he thinks Langdon has already made a dash for Australia, where he says Langdon has taken Que before.
"He's announced to many people, friends, family, that this boat will make it to Australia and back 10 times, no problem," Chapman said.
"Some people say the boat was heavily stocked to the gunnels with no room left ... and stores for over 30 days.
"It would be a challenging trip, and one I wouldn't do, and one many people wouldn't do. But someone with Alan's skills, could easily do it."
Langdon's 6-metre white wooden Tiki catamaran, which has blue anti-fouling paint under the waterline, is modified with a Bermuda mast, and sail ID number of T878, has a capacity to carry about 500kg in stores, Chapman says.
He estimates the crossing of the Tasman Sea in that vessel, which travels at about six knots, would take at least 30 days.
Calculating tides and winds, and depending on Langdon's tacking, the boat would currently be between 400 to 700 nautical miles off the New Zealand coast, he says.
"It's a big trip but once he crosses a line a couple of hundred kilometres offshore [of Australia], he looks like a coastal cruiser. He doesn't look like he's come from New Zealand in that little thing."
The pair could then easily hide in Australia, Chapman said.
Chapman says it's not the first time that Langdon has gone on the run.
In March last year the Langdon family of three - Langdon, Que and Wyler - was in Port Vila, Vanuatu, when Cyclone Pam struck.
The category 5 severe tropical storm battered the island, claiming up to 16 lives and sinking at least 20 boats.
It sank their 46-foot catamaran Sanyasin and the Langdons were lucky to escape with their lives.
After the cyclone, when the Australian and New Zealand air forces were repatriating people, Langdon took off for Australia with Que, Chapman says.
Chapman was enlisted by Wyler to find Langdon who kept moving about.
He says he eventually tracked him to the New South Wales town of Nimbin where Langdon and Que were living in a campervan on a large farm.
It's understood that Langdon and Que moved to Kawhia in August where they lived with local woman, Mary Smith.
She said the Langdon family had used her home as a base for years in between travels.
Langdon, a stay-at-home dad, built the catamaran the pair left Kawhia in on Smith's front lawn.
Smith raised the alarm on Boxing Day after Langdon and Que had been at sea without word for nine days.
She described Langdon as a competent boatsman who doted on his daughter.
"She was his best mate. He loved her to the max," Smith said.
Police this afternoon said that an RNZAF P3 Orion has searched the western coastline from Kawhia to Cape Reinga and the eastern coastline to the Bay of Islands, out to 35 nautical miles.
A Philips Trust Air Rescue aeroplane has searched from Mokau to Port Waikato, including harbours and coastline, out to six nautical miles.
Coastguard air patrol have searched, and continue to search, the bays and harbours on both coasts of Northland. Coastguard units have also searched Hokianga and Houhora Harbours.
Maritime NZ continues to broadcast police interest in the vessel on marine channels.
"Police are looking at a multitude of possible scenarios as part of this search, and this includes advising and liaising with Interpol, in the event that Mr Langdon has left New Zealand," a police statement said this afternoon.
"If you believe you have seen Mr Langdon's vessel in the last few days, or you think you may have information which would assist the search effort, please contact your local police station."