The adoptive grandmother of Alan Langdon is heartbroken the Kawhia man and his 6-year-old daughter Que have not been heard from since launching a six-metre catamaran at Kawhia Wharf on December 17.

Yesterday police sent out a spotter plane to search the coastline between Mokau and Port Waikato, but there were no sightings of Mr Langdon.

Mary Smith said she was not coping well with the possibility the sailing trip to the Bay of Islands could have ended in tragedy but said she was trying to stay positive.

"I'm not coping very well at all. I'm very sad, broken in fact."

Langdon and Que lived with Smith's "open home" in the tiny seaside village south of Raglan, where the 48-year-old stay-at-home dad built the catamaran on her front lawn.

Smith described Langdon as a competent boatsman who doted on his daughter.

"She was his best mate. He loved her to the max."

She said Langdon would do anything to protect Que, whose Swiss mother lived in Nelson but was currently in Switzerland on holiday.

Smith said she did not know if Ariane Langdon planned to return to Kawhia in light of the news but said it wouldn't be out of character for Langdon to be moored in a "black spot" somewhere without communication enjoying some fishing.

Before Langdon and Que set sail Smith slipped some Christmas presents and a letter into a bag for the pair and put it on board the white and blue catamaran.

"Hopefully they did open it on Christmas Day or whenever. It was just some clothes and lots of sweets of course which he doesn't like her to have too much of."

"We're hoping that they're safe and well. All we want is to hear from them, that they're ok. We can't do anything else."

Smith said sailing was the family's life and it was in the blood - Langdon's parents were also "sea people".

Langdon and his wife regularly sailed around New Zealand and the Pacific Islands according to Smith, before the couple separated.

"He knows the water. He's grown up on the water. Fished with his grandfather. Sailed the seas with his wife and daughter."

Langdon and Que had lived with Smith since the end of July after returning from overseas.

But Smith said the family had used her home as a base for years in between travels.

She described Que as a "beautiful" and "clever" child who was outgoing and well travelled.

"She's his best friend. He's a lovely father. He just talks to her, he doesn't growl or anything. And she gets on with everybody."

She said she "absolutely" loved Langdon and Que and would worry each time they left.

Smith and her cousin raised the alarm with the coastguard on Boxing Day, after Langdon and Que had been at sea without word for nine days.

"We must think positive."

An acquaintance of Langdon's, Ian Besley, said Langdon "owned the bar" at Kawhia Harbour he was such an experienced sailor.

Beasley said he was not concerned for Langdon because he had so much faith in his sailing abilities.

"I'm pretty sure he's just got no communications or doesn't want to communicate.

"Until the boat shows up I'm assuming he's just fishing somewhere. He would know how to live off the boat."

He said Que was "unnervingly confident" around the water.

Last year Langdon and his family had been in Port Vila in Vanuatu when Cyclone Pam struck.

Langdon's boat was damaged in the category five storm and Langdon reportedly rescued his daughter from the boat.

It's understood Langdon's father Walter and an uncle were also rescued from a boating mishap some 20 years ago.

At Walter and Kay Langdon's property just outside Kawhia sits the hull of an old catamaran.

The couple did not want to speak to the Herald.

Ali Moore, who went to school with Langdon and knows him by the nickname "Paddles", said Langdon regularly posted on Facebook but since he left there had been no word.

"I haven't seen any posts since he left. I just hope that he decided to go to Fiji."

She said Langdon was "laid back," but he loved his daughter and would not take any risks with her safety.

Langdon himself had suffered serious facial injuries in a car accident many years ago, Moore said, and he had battled ACC since.

"We're just all praying they're going to come home.

"It will be sad for the community if we don't find them or find out what's happened to them."