Water Safety New Zealand (WSNZ) recorded 90 preventable drowning deaths in 2023, with a spike in fatalities of children under five.
It said the statistics, from the 2023 Drowning Prevention Report, were concerning and it was working to identify areas of the greatest risk in the country.
The 90 drownings were slightly fewer than 2022's 94, however it was still greater than the 10-year average of 82.
WSNZ said 83 percent of incidents were males and 54 percent over 45.
"Alarmingly, the under-five age group saw a spike in drownings, with eight fatalities, surpassing the 10-year average of five," it said.
"Auckland experienced a concerning surge with 27 preventable drownings, surpassing both the 2022 figure of 17 and the 10-year average of 16."
SWNZ chief executive Daniel Gerrard said the trend in Auckland was "disturbing", and while the number of Aucklanders in the water and warmer climate contributed, it did not fully explain it.
Northland however experienced the opposite, with drownings dropping to 18 in 2022 to five in 2023.
"This improvement highlights the potential of targeted interventions and community engagement in drowning prevention," Gerrard said.
Gerrard said WSNZ was moving towards a 'black spots' initiative which identified the riskiest places for water activity in the country. He said the areas would be signed, similar to high crash risk areas on roads.
"By spotlighting these areas, tailored preventive measures can be put in place to save lives," WSNZ said.