Nearly twice as many women drowned last year than the year before, according to Water Safety New Zealand's (WSNZ) provisional figures.
A total of 88 people drowned last year, 10 more than the previous year, and 19 of those were women, up from 11.
"I can't sugarcoat it," Water Safety CEO Jonty Mills said.
"The water is our playground but it's incredibly unforgiving."
An early summer contributed to a spike in drownings late last year when warmer weather increased the number of people in and around water.
But Mills said the problem was more than a numbers game.
"Most of the time, it comes down to poor decision making. That's why most drowning deaths are considered preventable," he said.
New Zealand had a diverse and growing population who spent a lot of time in or near the water.
Mills warned of the widening gap between the water safety sector's ability to meet growing expectation and demand.
"Sector resources are stretched beyond their capability. This is a sector which relies on volunteers and is predominantly non-government funded."
Mills believed all Kiwis needed to take personal responsibility and was keen to work closer with local and central government. He said the huge spike in female drowning deaths as well as a jump in the under-5 age group - to seven from three - and drownings among the over 65s, which doubled from 8 to 16 deaths, were features of last year's figures.
"For under-5, the only foolproof solution is constant active adult supervision," Mills said.
"Also, we are living longer healthier lives and retirees are more active, which adds additional risk."
There were twice as many "accidental" drownings - when people had not intended to go into the water - last year than in 2016.
"This reinforces how important it is to think about water safety around any aquatic environment."
Preventable fatalities in Auckland doubled, jumping to 22, and the West Coast had the highest drowning rate per capita with six drownings.
Drowning is the number one cause of recreational death and the number three cause of accidental death in New Zealand, with a social cost of more than $400m a year.
"We need to educate more to ensure our kids are coming out of the system with the skills, competencies and risk awareness to enjoy the water safely, as well as run ongoing campaigns to create a long-term attitude and behaviour change around water," Mills said.
"We also need to secure the future of frontline water safety and rescue resources."
The Water Safety code applies to all forms of water based recreation: be prepared, watch out for yourself and others, be aware of the dangers and know your limits.