Search teams are scouring the Hutt River mouth and harbour after a teenager was washed away last night.
Police said the 19-year-old and a teenage friend went swimming in the flooded river around 10.30pm near Belmont School.
People are not listening, the message is not getting through and New Zealanders are drowning, Water Safety NZ says.
Thirty-one people have died since December 1 in summer drownings deemed preventable, the water safety body says. The last time numbers were this high was in 2011, when 35 people died over the same period. The toll excludes drownings after incidents such as suicides, murders and motor vehicle accidents.
This summer's toll includes seven people who died over a period of five days in the lead up to and on Waitangi weekend - including a toddler.
Water Safety NZ chief executive Jonty Mills said the wide range of people who lost their lives during the recent holiday period highlighted how complex the problem was.
"Water is part of Kiwis' DNA, it's part of our culture," Mills said. "[But] we need a culture change in this country around water. Similar to wearing seat belts and drink driving. That would look like a dramatic reduction in the drowning toll."
Mills said young men aged between 15 and 34 were particularly high risk, saying their high participation in water-based activities, a "she'll be right" risk-taking attitude and the way men tended to overestimate their abilities and underestimate the dangers were key factors.
Males represent around 85 per cent of preventable drownings and are four times more likely than women to drown in New Zealand.
In an effort to reduce the number of young Kiwi males lost to drowning, Water Safety NZ and ACC this summer launched an awareness campaign called The Swim Reaper.
Mills said the message had been really successful in getting out there, but people's behaviour was slow to change.
"We want everyone to enjoy the water but also want them to come home safely to their families at the end of the day."
Drowning is the fourth highest cause of accidental death in New Zealand - after vehicle accidents, falls and poisoning, a Water Safety NZ study has found.
Almost one-third of preventable drownings occur in rivers. And Mills said rivers were at high levels this summer due to heavy rainfall.
"Rivers are unpredictable and changeable, particularly after inclement weather."
The recent spate of drownings include Lower Hutt teenager Rory Smith who died after he was swept away by a swollen Hutt River trying to rescue his friend who had fallen in on February 2. His body was found washed up at Karaka Bay two days later.
On Waitangi Day 21-year-old Rachael De Jong drowned after being swept away on the Waikato River after the Aratiatia Dam floodgates opened sending waters of up to 90,000 litres a second downstream. Her body was later found in a rock pool.
The floodgates are opened several times a day and warning signs are in place alerting people not to swim in the area. A siren also sounds when the floodgates are opened.
A free diver died off the Otago Peninsula on February 3. Michael John Hodges, 35, was seen surfacing but then sank back under the waves.
Water Safety New Zealand chief executive Jonty Mills said a drowning costs around $4million in social, economic and community costs. Photo / Hagen Hopkins
Last Sunday four people died in water-related incidents.
A 70-year-old woman died after being swept out to sea while walking with her partner along the Kohaihai River, in Kahurangi National Park.
A 21-month-old boy drowned in a swimming pool in Makarau, north of Auckland.
A 30-year-old man was pulled from Wellington Harbour at Eastbourne unconscious. He later died in Wellington Hospital. And a male diver collapsed and died after reaching the shore at Anaura Bay, north of Gisborne.
Numbers have hovered between 90 and 113 drownings per year for the past five years with 108 deaths occurring in 2016.
National Life Saving manager Allan Mundy said there were around 1500 rescues by their 74 clubs on 82 beaches in 2016.
Those numbers could be down this summer after fewer people had braved chillier beach waters due to summer's wet and chilly start.
Around 85 per cent of lifeguard rescues were because of rips and holes in the surf.
Mundy reminded beach-goers to swim between the flags. In the 106 years New Zealand beaches have been patrolled no one has died between the flags, he said.
His biggest tip to any swimmer who got into trouble was to float on your back, put your hand in the air and don't panic.
"It might seem like 10 - 15 minutes is a long time but you can easily float for that time. If you're panicking you've only got one to two minutes before you burn out of energy and start to drown."
