Kiwi rescue officials have helped save the lives of four fishermen found cold and huddled together on the hull of their capsized boat.

Rescue Coordination Centre NZ organised the rescue of the men, whose catamaran CFV Salvation capsized at 3 am this morning in large swells, 25 nautical miles north-east of American Samoa.

The stricken group perched on the 10m fishing vessel's upturned hull and huddled together in the cold until daybreak.

In the morning light, the catamaran's owner swam under the capsized vessel and retrieved its Epirb locator beacon which he then set off.

The centre received the beacon alert from the vessel at 7 am today and began working closely with local rescue services and directing them to the location.

A police patrol boat from Pago Pago, which was carrying out training at the time, responded to the request and was on the scene in 45 minutes.

They found the people in the water and returned them safely to land.

All four were in good health.

"If there's anything to learn this situation it's that boat owners should consider a float-free Epirb," search and rescue officer Drew Coleman said.

"These people had also registered their beacon. It meant that when we received their alert we knew key details – such as who owned the vessel and their contact details – that helped us speed up this rescue and save their lives."

Rescue Coordination Centre NZ is responsible for a search and rescue region which covers 30 million square km stretching from Antarctica almost to the equator.