A shark lunged at a swimmer near a popular beach yesterday, forcing hundreds to flee the water as lifeguards closed the beach for the rest of the day.
The swimmer had to fend off the shark with a knife before reaching safety ashore.
Young mothers Nicky Kuka and Sandie Hine were wading at Mt Maunganui's main beach, looking after seven children aged 1 to 9, when the lifeguards' siren blared about 3pm.
"Holy s*** get my kids out of the water!" Ms Kuka said to herself, and ran for the shore with the youngest children.
Ms Hine, her friend, was further out and carried the older ones to safety.
Bay of Plenty surf lifesaving spokesman Mike Lord said that a man had come out of the water saying a shark had lunged at him.
The man had been snorkelling for shellfish when he was forced to use his knife to fend off the shark.
He was not injured in the incident.
"He got quite a scare," Mr Lord said.
He was not sure what type of shark it had been or how big it was.
Lifeguards said over loudspeakers that there had been an "attempted shark attack", and a crowd of about 300 gathered at the water's edge scouting the waves for fins.
Over-excited children pointed out 17 "suspected sharks", Ms Kuka said.
The lifesavers changed their terminology throughout the afternoon, to a "shark attack" at one point and later to a "shark encounter", all the time cautioning people to stay away from the water.
A surf lifesaving boat was sent out to check for dangers.
"We've been in the Mount for the last 15 years of our lives," said 15-year-old Steph Collins, "and there's never been anything like this before."
Fellow 15-year-old Terryn Duff said she had no doubt there were sharks in the water.
"There are probably another 10 sharks out there that they don't know about."
The beach remained closed an hour later when Judy and William Pegel arrived at the beach with their 3-year-old twins, Wendy and Marianne.
They saw the lifeguards' beach flags crossed - indicating the water was closed to swimmers - but took their children to the water's edge.
The family were wading in shallow water when Ms Pegel told the Herald she had no idea there had been a shark scare.
"We heard some announcement, but we didn't know if it was coming from the pool."
Laura Duff, 12, was one of the first to brave the water again after the scare.
She spoke to a lifeguard and was told the shark sighting had been around the Mount, away from the main beach.
"But I wasn't keen to go way out. I stayed around waist-deep water," Laura said.
The beach stayed closed past 5pm, and by then there were almost 100 people back in the water, including a few surfers.
Oscar Brisset, 10, said he had gone into the sea up to his waist.
"We knew sharks don't come really close to sand," he said.
His mother, Sylvie, said the water had been flat and they would be safe if they did not venture past the waves.
There was little panic at the beach, with parents relaxed enough to make black jokes that any shark would attack teenagers frolicking further out in the waves before coming to eat their young children in the shallows.
Witnesses said people had been slow to get out of the water when the siren had gone off - and were quick to get back in.
A woman enjoying a company Christmas party by the beach said she was shocked at how blase swimmers had been about the shark scare.
"If I heard that, I would get out of the water and not get back in."
Warm early-summer seas around northern New Zealand are attracting increasing numbers of sharks.
Angler Campbell Carter told the Bay of Plenty Times this week that he had never seen so many sharks off Tauranga, where makos, threshers, bronze whalers, sevengills and even the occasional great white shark could be found.
Department of Conservation marine scientist Clinton Duffy said sharks could be present anywhere in the upper half of the North Island where there were sandy open swimming beaches.