Police looking for a young girl who disappeared with her father are no longer physically searching for the pair, but say it remains a missing persons inquiry.

Photo: SUPPLIED

Sailor Alan Langdon and his six-year-old daughter, Que, have been missing for 17 days.

The pair left Kawhia Harbour in Waikato on a small catamaran on 17 December, possibly heading to the Bay of Islands.

Sergeant Vince Ranger said this afternoon that police had "searched all the areas we can physically search with the resources available".

That included the entire west coast from Wellington to Cape Reinga, and down the east coast to the Bay of Islands, he said.

"There's nothing to suggest anything near criminal has happened. Our interest and focus is on locating Mr Langdon and his daughter to ensure their safety.

"Interpol has been advised, and this was done early on. That they may be headed overseas is just one of many possible scenarios, and we're keeping an open mind."

The search for the pair had been made more difficult by the fact that Mr Langdon did not lodge an official trip report, he said.

"As such, at this stage our focus has been on searching New Zealand waters. We can't discount anything at this point. It's a possible scenario that he's headed for Australia, but we're keeping an open mind. For him to do so would seem foolhardy."

Earlier, Mr Ranger told Summer Report there had been many unconfirmed sightings of the pair, and every sighting was being treated as one of interest.

He still expected to find Mr Langdon and his daughter, he said.

"My expectations are that at some stage we will find Mr Langdon and his daughter. It's just a question of where he is and what his intentions really were."

On Saturday, police were focusing their search in Northland after reports a vessel similar to Mr Langdon's had headed in that direction in the past few days.

Col Chapman, a child recovery specialist who has been hired by Que's mother Ariane, said he believed Mr Langdon could be heading across the Tasman Sea, saying they could "easily disappear" in Australia.

Mr Chapman said he believed the pair's disappearance was another attempt by Mr Langdon to take Que to elude the family court system.

Que's parents have been separated for two years.

Her mother's attempts to reach a custody agreement had failed and a legal process had been started in New Zealand.