An elderly passenger has been winched from a boat far out at sea in a mission described by rescuers as “extremely challenging”.

The alarm was raised about 7.30pm on Friday with the national Rescue Coordination Centre tasking the Northland Rescue Helicopter due to its long range.

At that time the patient, who had suffered a serious medical event, was on board an 18m vessel about 130 nautical miles (240km) northeast of the Bay of Islands.

That put the rescue near the limit of the Sikorsky S-76 helicopter’s 270km range.

The chopper refuelled at Bay of Islands Airport near Kerikeri and reached the vessel at 11.15pm.

A paramedic was lowered onto the vessel and both patient and medic were winched onto the aircraft, which began the return flight to Whangārei at 11.40pm.

A spokesman for the four-strong crew said the conditions were “extremely challenging” but their training meant they were well prepared.

A Westpac Rescue Helicopter was deployed to Northland to provide emergency cover while one of the Whangārei-based choppers was out at sea.

The Northland Rescue Helicopter approaches the vessel about 240km northeast of the Bay of Islands. Photo / NEST

The vessel involved is believed to be the Patriot X, an 18m pleasure boat registered in Australia.

It was on its way to Northland at the time and is currently at Ōpua.

A paramedic readies the patient to be winched aboard the Northland Rescue Helicopter. Photo / NEST