Swimming around the capital of the country's largest island has been red-flagged for the rest of the summer even with warmer weather on the way.
Concentrations of bacteria 30 times in excess of the legal limit have been found in the water near Kuressaare.
The irony was not lost for participants in a safety day event held in Saaremaa's capital on August 14. ETV reported warning signs were out and red flags were flying.
Yet lifeguards had to go into the water anyway to demonstrate their lifesaving skills as part of the pre-planned event
Kuressaare city doctor Jüri Zabellevitsh, who has been monitoring the condition of the bathing water, said the first signs of hazard emerged in late July.
He said tests were conducted for two fecal coliform bacteria, which they found. The source is the nearby Põduste River, and as the exact origin could not be found within city limits, the Environmental Inspectorate, a national authority, will start investigating along the entire length of the river on August 15.
Zabellevitsh said the bacteria could be of human or animal origin.
It is not believed that the current conditions will be chronic, as seasonal winds can quickly change pollution patterns.