Grandparents killed in catamaran capsize as teen and father recover in hospital

A father and daughter are recovering in hospital after a catamaran capsized off the coast of NSW and killed three people, including the girl’s grandparents.

The 16-year-old and her 50-year-old father were about 12 kilometres off Stockton Beach in Newcastle when their 11.7m vessel capsized some time between 8am and 10am.

The catamaran departed Shoal Bay on Thursday morning and was heading south toward Ettalong Beach on the Central Coast when it overturned.

A man whose connection to the family was not yet known was killed alongside the grandparents, both aged 78.

NSW Police Acting Superintendent Grant Healey told reporters all five people were wearing life jackets at the time they were found.

Superintendent Healey said that decision likely went a long way to saving the lives of the two survivors.

Police carried a victim from the scene after the boat capsized Thursday morning. Source: 7NEWS Sydney

Just after 10am a signal from an Emergency Position Indicating Radio Beacon (EPIRB) was sent to the joint rescue coordination centre in Canberra sparking a rescue mission.

The father and daughter were winched out of the water by the Westpac Rescue Helicopter Service and taken to John Hunter Hospital and treated for hypothermia.

Rescuers had battled rough conditions as they attempted to retrieve them from the water.

Ambulance NSW Inspector Luke Wiseman said the rescue mission was complicated by high seas, strong winds and debris in the water.

It is unclear what caused the boat to capsize, but Superintendent Healey said the conditions were difficult.

"We had 25 to 30 knot westerly winds with the sea at one to two metres coming the other way. So it was fairly messy out there," he said.

NSW Police Marine Area Command Detective Acting Superintendent Grant Healey said the conditions were 'fairly messy'. Source: AAP

Authorities have not yet been able to recover the overturned catamaran, which has drifted out to sea.

"As soon as there is favourable sea conditions there will be an attempt to salvage the vessel," Superintendent Healy said.

"But whilst the weather is like it is, all we can do is let the boating community know where it is."

A strong wind warning is in place along the NSW coast, from the Hunter down to Eden.

Roads and Maritime Services are urging fishers and boaties to be extra cautious, with choppy conditions expected on exposed bays as well as dangerously rough conditions offshore.

- with AAP

Do you have a story tip? Email: newsroomau@yahoonews.com.

You can also follow us on Facebook, download the Yahoo News app from iTunes or Google Play and stay up to date with the latest news with Yahoo’s daily newsletter. Sign up here.