Alan Langdon, 49, and his six-year old daughter Que Langdon have not been seen or heard from since December 17. Photo / Facebook
The disappearance of a yachtie and his six-year-old daughter who left Kawhia Harbour 11 days ago has been described as a "bit of a mystery" and left family "very worried".
Alan Langdon, 49, and his daughter, Que, left Waikato's Kawhia Harbour for the Bay of Islands on a catamaran on December 17 and have not been seen or heard from since.
A family member posted on Facebook that they were heading to Paihia to visit friends for Christmas Day.
"We are very worried."
Police say they have grave concerns for their welfare and are seeking information from other boaties who may have seen them.
Asked if police believed there were any suspicious circumstances surrounding their disappearance, a police spokeswoman said they had no further information to add.
Local marine contractor Alan Rutherford said sea conditions have been "pretty bad" over the last ten days.
"It's a bit of a mystery... If you were sailing in a little cat like that you'd want to know what you were doing."
Waikato Search and Rescue, along with the Auckland Maritime Unit, continue to make inquiries and are calling for any information or sightings of the pair or their boat.
"Mr Langdon is an experienced and capable skipper, and his daughter has had experience on boats also," said Sergeant Warren Shaw, of Waikato Search and Rescue.
"We continue to appeal to the public for anyone who saw the vessel - a 21ft [6m] white catamaran with blue anti-fouling paint under the waterline - in the Kawhia Harbour, crossing the Kawhia Bar, on the afternoon of December 17, or any sightings since, to call police."
Coastguard has asked for sightings of the catamaran with a sail ID number of T878.
Langdon is believed to be estranged from his wife. It was reported yesterday she returned to her home country of Switzerland after their split last year.
In March last year, Langdon, his wife and Que were 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.