One in 10 leisure spots on Canterbury's coast are unsuitable for swimming, including an "appalling" Banks Peninsula beach that will be visited by tens of thousands of international tourists this summer.
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However, popular swimming spots including Gore Bay, Sumner Beach and Woodend Beach were among the nearly 90 per cent of Canterbury coastline sites rated fair, good or very good in the Ministry for the Environment's recreational water quality report, meaning they were safe for taking a dip.
Akaroa's main beach was dubbed "poor" and "generally unsuitable for swimming".
Harbar Beach Bar owner Rick Velenski, whose business is directly opposite the beach, said the dirty water was unlikely to impress the 200,000 cruise-ship visitors expected to visit the Banks Peninsula town this summer.
"I've been out on the boats and there's been raw sewage around, floating close to the harbour - it's just appalling.
"As soon as you bang a sign up there [on the beach] with people from 86 cruise ships walking past, it doesn't go very well, because it's all about the beach and the water."
Velenski said the pollution made "a complete mockery" of New Zealand's clean and green image.
The region's freshwater recreational sites also came under the ministry's spotlight in the report, with 45 per cent dubbed either "poor" or "very poor", meaning they were unsafe for swimming.
At one of the dirtiest freshwater spots, Kerrs Reach on the Avon River, rowers use bleach on their oar handles to ward off infections.
The waterway, home of Canterbury rowing, was rated "very poor", meaning swimming is "unsafe".
In Christchurch, Canterbury Rowing Club captain Mike Petherick said clubs took precautions to ensure their rowers were safe.
"We have bottles of hand sanitiser on site for people to use, and we spray the oar handles with bleach to stop any blisters getting infected."
The ratings are based on data acquired over five consecutive summers from 210 freshwater beaches and 248 coastal beaches.
Sixteen per cent of New Zealand's coastal beaches were rated poor or very poor, and 45 per cent of lakes and rivers were also deemed unsafe for swimming.
Green Party environment spokeswoman Eugenie Sage said the Government needed to get serious about cleaning up New Zealand's swimming spots.
"Kiwis heading down to their local swimming hole should not have to worry whether it is safe to swim or not. We are selling an image of 100 per cent pure but the Government is not prepared to invest in making that image real."
The ministry's report was based on World Health Organisation guidelines. Canterbury medical officer of health Dr Alistair Humphrey said the standards were so high that in some countries no beaches made the grade.
"We are fortunate that we have good-quality beaches that we can use."
Environment Minister Amy Adams said the trend was one of "slight improvement", but the results could still be better.
"Our water quality is good by international standards and most of our popular sites are fine for swimming, but that's still not good enough. My preference will always be for all our sites to be safe for swimming."
Adams said the Government was working with councils and communities to find "enduring solutions" to the issue.
- The Press
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