A world-class Gisborne surfing spot and one of Northland's most picturesque strands of coastline are among more than 40 swimming beaches hit with a "caution" label for water quality.
There is what Labour's environment spokeswoman called a "disturbing" risk of at least 10 per cent of people becoming sick after swimming at about 14 per cent of 350 monitored beaches in the country.
The high-risk ratings, based on an overall measure taking in three years of data, have been revealed in a newly expanded website launched by authorities and giving a comprehensive picture of water quality in New Zealand.
The poorly rating beaches include Makorori, near Gisborne, which boasts a significant surf break, and pohutukawa-lined Coopers Beach, one of the most popular swimming spots in Northland's picture postcard Doubtless Bay area.
Both had three-year caution ratings, although the water quality was considered acceptable at the last checks earlier this month.
Others on the list included Opononi in Northland, Taranaki's Oakura Beach, where thousands of sun-seekers congregate at the region's annual New Year's Day Beach Carnival, and three sites at popular Island Bay in Wellington.
Caution-labelled Auckland beaches include the central Judges Bay swimming spot, which people were asked to avoid at one point last summer after high levels of bacteria were found, and French Bay, which is popular for canoeing and picnics.
In the Auckland region, poor water quality at beaches was typically due to overflows of sewage from the wastewater network and significant pollution of the stormwater system.
The Auckland Council advises swimmers to stay out of the water for up to 48 hours after heavy rain, obey warning signs and avoid high-risk areas such as stormwater outfalls and stream mouths.
The beaches which feature on the coastal section of the website Land, Air, Water Aotearoa (Lawa) are checked by regional councils for levels of enterococci, an indicator for bacterial contamination.
Sixty-four per cent of beaches had risk ratings of low or very low, while the remainder were considered generally acceptable for swimming.
Environment Minister Dr Nick Smith, who launched the expanded website at Wellington's Oriental Bay yesterday, described the country's beach water as "generally very good".
"We've got 64 per cent of beaches where the risk of getting unwell is incredibly low, and 22 per cent on top of that have an acceptable standard," he told the Herald.
"It really is only 14 per cent where we do have a problem."
But Labour environment spokeswoman Megan Woods said it was disturbing that some of our favourite beaches were now classified as high-risk.
"This will come as a shock to the generations of New Zealanders who have holidayed at places like Coopers Beach and Opononi," she said.
"It isn't good enough. The Government needs to be doing more to ensure that these high-risk beaches are cleaned up."
Green MP Catherine Delahunty said the figures were not good news at a time many Kiwis were heading off to the coast. The Government could help improve beaches by offering more subsidies for sewerage schemes for beach communities, and cleaning up fresh waterways that flowed to the coast, she said.
Environmental Defence Society chairman Gary Taylor said the responsibility belonged to regional councils.
"If there are non-compliant sites, then the regional council is at fault and needs to act."
Dr Smith said the Lawa website, which allowed people to check their local beach for both the latest readings and its three-year rating, would help improve the situation.
The initiative had been jointly created between regional councils, the Cawthron Institute, the Ministry for the Environment and the Tindall Foundation.
"This new website, and the openness and transparency of this data, will actually help focus those communities that do have poor water quality on things they do need to change, so that their communities as well can enjoy good water quality," Dr Smith said.
Although the beach water quality in some parts of the country was "not as good as we would like", the Government was more concerned with improving the state of rivers and lakes, he said.
Figures released this year showed nearly two-thirds of monitored river sites were unsafe for swimming, a third of lakes were unhealthy and 39 per cent of native freshwater fish were now considered threatened.
Freshwater data from 1100 monitored sites, launched on the Lawa website in July, showed both improvements and deterioration in water quality attributes such as phosphorus, nitrate-nitrogen and E.coli.
Rivers and streams around urban areas tended to have the poorest water quality, although this was generally improving.
Dr Smith said the quantity and quality of environmental data would next year be expanded with the passing of a new Environmental Reporting Act.
"It really is going to provide robust information for New Zealanders and for visitors in exactly how New Zealand matches up to its clean, green brand," he said.
"There will be, as we implement the act, a bit of argy-bargy over exact messages and those sorts of things, but in my view, it's just like with GDP, inflation and other economic measures - we do need to invest more in measuring how well we look after our precious environment."