A father has died and two of his children are in hospital after swallowing water as the trio waded to shore after they had been fishing.
They had been caught in the incoming tide off Awhitu Regional Park in southwest Auckland.
The park is on the Manukau Harbour side of the Awhitu Peninsula.
Awhitu Volunteer Fire Brigade chief Andrew Hamilton told the Herald the father, and his daughter and son, were returning from a small island, Kauritutahi, in the harbour about 200m from the beach at the regional park.
"Special mention must be made of the campers there," he said.
"They were alerted to it before we got there and went out and helped the family in to shore."
Police were called to the scene at 12.40pm following reports three people were in trouble in the water.
The father died at the scene. The children had swallowed some water and were flown by the Auckland Westpac Rescue Helicopter to Middlemore Hospital in a moderate condition.
Hamilton understood the father and children were camping at the regional park with other family members.
"I think they were fishing on the island … They got caught in the tide when they were making their way back to shore by foot."
The island is about 200m from the shore.
"They are big tides at the moment with a lot of current when the tide is coming in and going out."
A spokesman for the rescue helicopter said: "When crew got there, CPR was in progress on an adult male patient. He unfortunately died at the scene.
"Crew of Westpac 2 assisted two children who had been rescued prior to the rescue helicopter arriving at the scene."
The spokesman said intensive care paramedic Russell "Rusty" Clark attended the incident.
He had also attended a rescue in West Auckland's Waitakere Ranges yesterday, in which two teenagers died.
The teenagers, and three friends were swept up by a flash flood.
The five boys, all from Auckland and aged 17, had been swimming at the Cascade Falls area in the Waitakere Ranges when heavy rain struck around 4.15pm yesterday.
They had tried to scramble on to rocks before attempting to cross to the other side to reach their vehicle. Two had made it to the river bank but three were swept away.
One then ran to a nearby golf course to raise the alarm. He was taken to Waitakere Hospital with mild hypothermia.
One of the trio swept away managed to grab hold of a tree on the bank of the stream, and was eventually winched to safety by the Westpac Rescue Helicopter about 7:15pm.
Two of the boys were found dead, Inspector Fata Willi Fanene said. They have been identified as Sosi Turagaiviu and Mitch Woolley, both 17.
At about 6.40pm Sosi Turagaiviu, of Massey, was found in the water under a bridge on Bethells Road, near Te Henga Rd, Fanene said.
Then, at about 7.50pm, the body of Mitch Woolley, from Waitakere, was located by search and rescue teams in the Cascade Falls area near where they were swimming.
Fanene said the boys' families were "very distraught".
"We have been talking to the families of the victims of this tragic incident, and we are ensuring they are supported through what is an incredibly trying time.
"We are also making sure the three other young men who were caught up in this event are looked after, as this has been a very traumatic experience for them and their families.
"An incident like this is an awful reminder of the power and unpredictability of our natural environment."
It was not clear if the boys had been aware of the impending storm that struck the area yesterday, Fanene said. It was concerning that people had been out swimming when there had been warnings about sudden rainfall.
The Auckland Westpac Rescue Helicopter was called at 5.30pm to help with the search and rescue operation.
Pilot Rob Arrowsmith said he, crew member Ati Wynyard and intensive care paramedic Russell "Rusty" Clark initially believed they were rescuing two people who had been swept away - but on speaking with them realised there were another three missing.
The normally gentle Cascade Falls had swollen to look like "Huka Falls in a picturesque bushy valley", he said.
Worst in 30 years
A Piha park ranger said last night's torrential rain and flash flooding was the worst, and fastest, flood he has seen in 30 years on the job.
Roads were completely covered within half an hour, with cars swept along in the floodwaters, Auckland Council ranger Andy Peterson said.
A MetService weather station recorded 27.5mm of rain at Piha between 5pm and 6pm last night.
Another Waitakere weather station reported 43.5mm of rainfall in an hour.
A group of 20 people were trapped for three hours at Kitekite Falls near Piha yesterday. The falls are a short, easy walk from the carpark but a flash flood made the river impassable.
On Glenesk Rd, which leads to the falls carpark, about 100 people were evacuated from their homes.
Peterson told NZME it was "incredibly lucky" the tide had been out at the time, allowing the water to recede quickly.
Sixty people were evacuated by boat down the two-metre-high waters running down a Piha road yesterday evening.
The church group was taken from Piha Mill Camp, on Glen Esk Rd, by the surf club's inflatable rescue boat.
Camp owner Peter Kruger said the water in the Kitekite Stream rose up within half an hour as high as his knees, and it was all gone again within another 40 minutes.
Kruger said locals of 30 years have never seen the stream rise so quickly.
Piha's Deputy Fire Chief Ron Gorter said he was pushing floating cars off to the side of the road to allow the inflatable boat laden with evacuees down the street - or in this case, river - to safety.
A local for 25 years, Gorter says he's never seen the water rise so quickly.
He says the overflowing river rose one metre in 20 minutes.
A 150-metre stretch of Glen Esk Road was under two metres of water - up to the headlights of the fire truck trying to get through.
Gorter said the rain came down "really, really quickly".
"We got 10,000 litres in our water tank in half an hour, which is massive. It was a very intense weather pattern."
Kruger said the cleanup starts today after suffering significant cosmetic harm - but thankfully no buildings have any structural damage.
He says a few washing machines and dryers are gone, but the dormitories are completely unharmed.
The river is flowing calmly this morning but there is evidence of the floodwaters, with gravel and bush debris high on the riverbank and flax bushes sprawled across road signs.
The Piha community is now out in force beginning a tough clean up job.
An NZME reporter in the West Auckland village said there were tears, long faces and grimaces as neighbours checked on each other and offered hugs or a hand.
Cars are soaked through - doors flung open, seats still sodden. Many owners are too scared to try start them.