An Auckland couple without lifejackets battled rough surf for 20 minutes yesterday after their 5m boat flipped and sank outside Tairua Harbour, on the Coromandel Peninsula.

Senior Constable Ian Fredericksen, of Tairua, said the man, aged 60, and woman, 50, from Torbay, were returning from a diving trip at Mayor Island, 30km off the mainland.

The couple's aluminium craft was moving slowly outside the ring of breakers at the harbour's sandbar waiting to cross into calm waters.

But a large wave from behind broke over the boat, capsizing it. The occupants were flung into the sea about 500m from shore.

Their plight was seen by dozens of people on Paku Hill and Pauanui Beach.

Jenny Till, whose holiday home overlooks the bar, saw the boat overturn and called emergency services.

"The couple were holding on to the boat for some time and then a wave came and one of them lost their hold. Soon none of them was with the boat."

The couple were eventually taken on board the Pauanui jet rescue boat, and an inflatable craft manned by Pauanui Surf Life Saving Club members.

Surf patrol captain Gareth Brittell said it took 10 minutes searching to find the woman in the rough 3m surf. The jet rescue boat found the man about 400m from shore.

Senior Constable Fredericksen would not name the couple.

He said the man argued that lifejackets were not necessary because their full wetsuits gave sufficient buoyancy.

Mrs Till said yesterday's bar conditions were treacherous for small craft, with breakers sweeping the full width of the harbour entrance.

Her family had called rescue services a dozen times to mishaps at the bar during 20 years of holidays.