A teenage boy who disappeared in the sea at an isolated Auckland beach yesterday saved the woman trying to rescue him by letting her go as he was swept away.

The woman, thought to be a relative of the 16-year-old who went missing at Whatipu yesterday, had rushed to help after the boy got stuck in a rip around 1pm.

"She swam out to him and they both got dragged out together," said witness Leah Lutau.

"The young boy released her, he said go, he pushed her away. Then she was drifting in the water as well."

Lutau, who heard the boy cry out for help while she was swimming but couldn't leave her children, said those on the beach were shouting advice to the woman as she struggled.

"We said, float, float, lie on your back and she managed to swim in."

Lutau said the boy drifted further and further out. "And then he just went under until we couldn't see him any more."

Around 1.30pm, a call was made to emergency services. Huia fire brigade was first to arrive, followed by lifeguards from Karekare - the nearest manned beach - with jet skis and inflatable rescue boats.

The boats scoured the area between Ninepin Rock and Patitutai Island, where the boy was last seen. Photo / Michael Craig

Whatipu, a black sand beach on the north side of the Manukau Heads known for its strong currents, does not have its own surf lifesavers. It is also isolated, an hour's drive from Auckland down a windy, unsealed road.

Two Coastguard vessels, the Westpac Rescue Helicopter, and several local boats joined the search, largely focusing on the area between Ninepin Rock and Paratutae Island where the boy was swimming.

The woman who tried to save the teen was taken back to Auckland by St John Ambulance. Another woman was also treated by paramedics after she collapsed. The rest of his family waited, distraught, at the water's edge.

One man, thought to be his brother, refused to leave even after most of the rescuers had gone.

Police said one person was kept in hospital overnight for observation and that the search will resume this morning with Land Search and Rescue and the Police Eagle helicopter.

This morning, police said the search would resume at 8.30am.

"Emergency services were notified at 1.30pm yesterday that a teen had entered the water and not come out. Search teams were deployed immediately and worked until dark but unfortunately did not locate the missing swimmer.

"Police, SAR and other volunteers will be continuing a shoreline and water search today."

A family member said they were having a barbecue at the campground nearby when they heard the boy was missing.

"We came down straight away when we heard he was swept out," he said.

As she was leaving the beach, Lutau said she would take her children home to talk to them about what had happened. "They don't really understand yet," she said.

The woman who tried to save the boy is helped to a waiting ambulance by paramedics. Photo / Michael Craig

Over the last seven days there have been three other drownings so far - a man in Lake Taupo on Christmas Day, a free diver in Wellington on December 23, and a 20-year-old man who got into trouble while swimming at Maraetotara Falls in Hawke's Bay.

Last summer, eight people lost their lives in drowning incidents that Water Safety New Zealand deemed "preventable".

Yesterday's tragedy came just a day after an off-duty intensive care paramedic helped save the life of a man who got into trouble in the water at Cooks Beach, on the Coromandel.

A 30-year-old had earlier jumped into the water but didn't resurface early Friday evening. The paramedic rushed to his aid, pulling him from the water.

Two ambulances and the Auckland Westpac Rescue Helicopter responded to the incident, with the man being airlifted to Auckland City Hospital, where he was yesterday in a critical but stable condition.

Meanwhile, the dramatic rescue of two pregnant women from surf north of Auckland has been cited by lifeguards urging their service be granted increased resources and funding.

Surf Life Saving Northern Region chief executive Matt Williams told the Weekend Heraldyesterday that a funding injection of more than $9 million was needed over the next three years, for essential upgrades of the region's clubs, digital infrastructure and gear for volunteers.

Without it, he feared lives may be needlessly lost at some of the region's popular swimming and surfing spots.

Talking to the Herald on Sunday, Orewa lifeguard Faron Turner has spoken of the workload guards at his base face - including recalling the January 28 rescue of two pregnant women, and a friend, last summer who had become caught in choppy water in a cove between Red Beach and Orewa.

Whatipu, on the northern edge of the Manukau Heads, is known for its strong currents and rough seas. Photo / Michael Craig

Turner said it was thanks to staffing and adequate resource that they were able to get to the women in time.

"That terror was in their eyes right up to the point when they were on the beach," he said.

"It was probably still very close to those minutes between success and failure."

While the rescue unfolded, other guards were assisting with a mother who had fallen and broken her ankle on the beach suffered while chasing after her child.

Turner said the nature of the busy day at the beach - and the two simultaneous incidents - highlighted how important it was to have a full team of lifeguards on deck.