According to the latest report (2013) just published by the Ministry of Environment, Energy and Climate Change on the quality assessment of Greek bathing waters, you could practically drink it at 94% of the sampling points, as they have been classified as “excellent quality”. In fact, you would have no problem enjoying the sea throughout Greece, as 99.8% of the sampling points have been assessed as suitable for bathing, according to the European Directive 2006/7/EC.
The assessment involves the evaluation of microbiological parameters in more than 2150 sampling points throughout Greece and the statistical analysis of the results over a 4-year period.
You can find out more about the quality assessment program of the Greek bathing waters at http://www.bathingwaterprofiles.gr/en and the full report for 2013 is availabe at “Bathing Water Quality in Greece”.
Please enjoy them responsibly!