Flying sharks have taken off, causing air traffic alerts and slowing traffic on a busy highway.
The Air Swimmer sharks are 1.4m-long helium-filled balloons directed by a remote control.
They were "extremely popular" Christmas gifts, said retailer The Warehouse, and reports of their escapes started almost as soon as presents were unwrapped.
Kim Clarke said her inflatable fish did not even make it to gift-giving.
"I went to get it filled, got it to the car, made it home - but as I got [it] out of the car, it was very windy. I tried holding on but [it] was gone," Ms Clarke said.
Hamilton resident Brian Thompson lost his shark on Christmas Day, before his grandchildren had had a chance to play with it.
He inflated it in secret during the morning - but it floated through the kitchen and lounge, up a flight of stairs and across a bedroom before leaving through the bedroom's external door.
"They're cunning characters, these sharks," Mr Thompson said.
The first mid-air encounter happened on Boxing Day.
A plane was 10km south of Christchurch at about 600m on a landing approach when it passed within 100m of a shark, said Civil Aviation Authority spokeswoman Emma Peel.
Hamilton pilot Evan Yates said he flew past one in his small Robin aircraft two days later.
"I thought it was a helicopter but then I noticed it's got fins and a tail!"
Ms Peel said the sharks were not a worry to pilots. Their components - a thin balloon and a plastic control package - did not have enough mass to damage an aircraft.
Airways Corporation spokeswoman Monica Davis confirmed there had been at least two alerts over airborne sharks, but said the agency was still collating nationwide data.
A Bay of Plenty motorist said a shark was seen near a major highway, causing traffic to slow.
"We were driving down the main highway and I saw one of these above a paddock," said Trade Me user Megan.
"The traffic had slowed down to 60km/h."
December 25: A shark escapes from a Howick home, another flies away from Hamilton.
December 26: A Christchurch pilot spots a shark from his plane window.
December 28: A Hamilton pilot encounters a shark mid-air and circles it.
December 31: A shark sneaks through a Pukekohe ranchslider, traffic slows on a Bay of Plenty highway to watch a shark hovering over a paddock, and another is sighted in Napier.
- APNZBy Michael Dickison Email Michael, Hayley Hannan Email Hayley