Shocking new data has revealed 67 percent of all drowning fatalities last year were adults over 35.
Water Safety New Zealand (WSNZ) says adults continuously "overestimate" their abilities when it comes to water.
The Drowning Prevention Report 2018 was released on Wednesday and it shows a rising trend of adults drowning in preventable situations.
A preventable drowning is one where water safety could have stopped a fatality.
Non-preventable drowning includes events such as homicide or vehicle accidents where education would not have made a difference.
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"Adults in this country continue to overestimate their abilities and underestimate the risks when it comes to water," said WSNZ CEO Jonty Mills in a statement.
"The high rate of incidents involving drugs and alcohol is a concern," he said.
"Alcohol, drugs and water-based activities do not mix and can be a fatal combination."
Despite the rise in older people drowning, the total death toll has dropped from 91 in 2017 to 66 in 2018.
Deaths resulting from boating accidents have dropped significantly, too. In 2017, 19 people drowned while boating and, in 2018, that number plummeted to six.