More than twice as many children aged under five drowned in 2017 compared to the previous year, a figure Water Safety NZ says is concerning.
At least 86 people drowned in 2017, up from 79 the year before.
Water Safety NZ chief executive Jonty Mills said seven of those drownings were children under five, up from three in 2016.
He said that was a concerning statistic.
"The really only fool-proof solution there is that constant adult supervision," he said.
"There really is no other solution, so that's been a concern."
Mr Mills said the number of women who drowned this year had doubled, a reflection of high participation rates in water-based activities across the country.
He said that historically it was men who made up most of preventable drownings.
The preventable drowning toll for the official holiday period was three, five fewer than last year.
Mills said the holiday result was encouraging, as the sector was bracing for a busy season because of a dry, hot weather at the start of summer.