It has been the worst summer so far for drownings in New Zealand since 2015, according to Water Safety New Zealand.
As of January 3, there had been 22 drownings across the country since the beginning of December, with another two months to go before the end of the summer reporting period.
Last summer, 25 drownings were recorded across the whole three-month period, which is also the average over the past five summers.
Twenty people drowned in the month of December 2021, more than double the figure for the previous December, when there were nine.
Water Safety New Zealand chief executive Daniel Gerrard said the uptick in fatalities was "unprecedented".
"We have to start making some of these calls ... this is the worst we've had the last six years," he said.
"We're up to 22 and we've still got two months to go ... last year was 25 total so there's absolute alarm bells."
It comes after two men drowned in the Manawatū River on Sunday, bringing the total of drownings in the Ahimate Reserve to four in less than a week.
Gerrard said a common theme in drownings was people underestimating the conditions and overestimating their ability, but wondered if lockdown restrictions last year had accentuated this further.
The months-long lockdowns for Auckland, Northland and Waikato may have encouraged people to try things they hadn't done before, overestimate their fitness or delay the servicing of equipment.
"I do think the bulk of us being locked down for such a period of time, maybe our fitness isn't what it had been.
"In line with that it could also be dive equipment, or your motor in your boat ... and you're out somewhere and potentially your equipment fails.
"We're hearing a lot of that anecdotal stuff, that dive equipment is not serviced."
On top of this, lockdown restrictions had disrupted the school year for primary school students, affecting the pool sessions and water-safety skills children were usually given in term 4.
"They also go home and share some of that info with Mum and Dad, so it's all more front of mind and more topical at this time of year – and that hasn't happened in Term 4 this year."
There had also been a general uptick in river drownings, with 24 river fatalities in 2020, an increase compared to the 2014-2018 average of 17.
This had dropped to 16 in 2021 but Gerrard said rivers were generally a more dangerous environment than beaches, as they could change quickly with the weather
"There are just so many variables associated with rivers ... a flood can come through and scour out different parts of the river that completely change it."
It has been a particularly deadly week at the Manawatū River in the Ahimate Reserve, Palmerston North, where four people have drowned since December 29.
Two of them – an 11-year-old girl and a 27-year-old woman - were members of the Myanmar refugee community. A givealittle pagee to support their families has already generated more than $40,000.
Palmerston North City Council and police are now urging people not to swim at the reserve, and a council spokeswoman confirmed on Monday afternoon "no swim" signs had been erected.
Palmerston North resident Georgie Rynhart recalls a near miss she and her family had at the river several years ago, in what she believes to be a similar spot the recent drownings occurred.
"I never thought it would be unsafe because there were other people swimming there, but after our experience we were not going to go out there again."
Rynhart's family were enjoying a walk and quick swim at the Ahimate Reserve on Christmas Day 2017 when her daughter, a strong swimmer, was pulled under.
"Our 9-year-old got into trouble on the way back and we didn't know until the older one got the whole way across and told us that she was in trouble."
Rynhart's husband was able to rescue their daughter but said it had been more of a struggle than expected.
"It happened so fast. It was so quick and so quiet," Rynhart said.
"If we hadn't been told, she would have just gone under and we would have realised she was missing."
Rynhart said the river appeared deceptively calm from the shoreline.
"The river looks lovely from the surface but it's what's underneath that's the problem," she said.
"If you're on the beach part and you walk out, it drops off very very suddenly.
"And people aren't aware that every time the river floods, it changes – the ground will shift, and logs move or get pulled forward, underneath where you can't see."
Rynhart said at the time they had wondered if they had simply been unlucky, but following four drownings in less than a week more stories of near misses like theirs had surfaced.
Yesterday, Palmerston North man Matthew Brougham spoke to the Herald about a near miss at the river on Christmas Eve, just a week before several people drowned at the same spot.
"When it's a 9-year-old, you think maybe it's because they're little," Rynhart said.
"But when grown men, confident swimmers are having the same trouble in the same spot, it's a major red flag."
Daniel Gerrard urged the public to think carefully about where they chose to swim this summer.
"You need to know the environment you're going into, and watch out for yourself and other people so you're not overestimating your own ability," he said.
"[It's about] making sure you think before you jump, and if in doubt, stay out."