The beach, also one of Phuket's longest, records six ''excellent'' ratings in measurements taken six times between October 2008 and August 2009.
It's the only beach in four years of testing to record what amounts to a ''perfect'' score.
There is just one problem: Karon is also one of Phuket's most dangerous beaches, with the drowning toll especially high during the monsoon months between May and October.
And even in high season when the waters are more tranquil, there are no lifeguards on Karon or for that matter any of Phuket's popular beaches. All beaches have been unguarded since mid-November because of a flaw in Thai law.
So in theory, if you get into trouble while swimming off Karon, you will know that you are about to drown in the island's best-quality sea water.
Black jokes aside, the latest figures on water quality, sampled from beaches all around Phuket, show a continuing decline in quality, with Karon as the most dramatic exception.
Dr Somkiat Khokiattiwong, of the Phuket Marine Biology Centre, attributes the decline in quality to construction projects with uncontrolled run-off, as well as household waste water that flows to the sea.
After rain, the water quality usually drops markedly because earth and waste are carried into the ocean.
December is by far the best month in which to swim, with 14 of the 23 beaches recording blue ''excellent'' stars at that time. Green ''good'' stars are still present on most beaches most of the time, although Phuket's west coast is generally better rated than the east coast.
Yellow starts signifying ''bad'' appear just three times in the latest measurement figures, once at Kamala in October and twice at the beach closest to Saphan Hin, the island's rubbish dump, in October and June.
Light blue stars signify ''mediocre'' water quality. So far in four years of testing, no Phuket beach has recorded a ''very bad'' red designation.
Three sets of measurements are taken on Patong beach, and back in 2006, Patong recorded three yellow ''bad'' stars out of a total of 18. However, there were only blue and green stars in the latest figures.
Generally though, Dr Somkiat says water quality at Phuket's beaches is in slow decline.
''Government controls on construction and household waste need to improve,'' he says. ''More attention needs to be paid to improving the quality of waste water.
''Some resorts are still not prepared to spend the money on the equipment they need to buy to preserve the environment so guests keep coming back.''
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Can we get a list of those resorts? Perhaps we can post them on Trip Advisor. Wasn't it previously mentioned that Club Med is one of those resorts? Just look at the back and see the sludge going into Kata!
Posted by VFaye on February 12, 2010 10:56