Most people generally drowned offshore, rather than in rivers or ponds, while immersed in water, collecting shellfish, free and scuba diving, or in a harbour.
Eight people drowned in Northland waters at the same time last year and 17 for the whole of 2016. Twelve people died from drowning in Northland in 2014.
Mr Mills said Northland was a critical area for his organisation in terms of running awareness programmes with other stakeholders such as Sport Northland.
"We do know Northland gets a huge influx of people from Auckland and other parts of the country during summer so they need to be made aware of the conditions before getting into the water,'' he said.
"Northland has a disproportionately high number of drownings and the key message is for people to be aware of their abilities and to watch others and if they are boating they should check the conditions."
Mr Mills said each year 20 recreational boaties lose their lives throughout New Zealand and at least two thirds would not have drowned if they wore lifejackets.
The same message applied to those intending to get into Northland waters this summer, he said.
"Generally an under-estimation of the risks and an over-estimation of ability to manage those risks is a key contributor to drowning. This has to change."
Mr Mills said by taking a more realistic and responsible approach, and learning aquatic survival skills, people could safely enjoy the country's wonderful waterways and go home at the end of the day to talk about their experiences.
Northland's 2016 total drowning toll was almost twice its five-year average from 2011 to 2015, and the highest since 1995.
Water Safety NZ has included in last year's Northland drowning statistics eight people who drowned in the Kaipara Harbour tragedy in November.
The Northland Regional Council has clarified the incident took place on the Auckland side, hence could not be counted in Northland's drowning statistics.
Water Safety NZ is seeking a formal clarification on whether the accident happened in Northland or Auckland.