Fans of open water swimming in the Lake District are advised to avoid two locations.
Crow Park at Derwentwater and the Boating Centre at Coniston have both been given poor ratings in the latest results of water quality testing.
Both were designated as bathing waters only this year and were among 450 sites regularly used by swimmers.
The tests monitor for sources of pollution known to be a risk to bathers’ health, specifically E coli and intestinal enterococci.
Other sites in Cumbria, including Windermere, Walney, St Bees, Allonby, Seascale and Haverigg, were rated as either good or excellent. Coniston Water’s Monk Coniston was rated as excellent and Brown Howe was rated as good.
The Government said the poor ratings for Derwentwater and the boating centre were not unexpected. They were among 18 of 27 new sites listed for this year.
It said: “The new sites have not been managed for bathing before, and it takes time to understand and tackle the sources of pollution affecting them.”
Following the results, the Environment Agency said it was working with local partners to take targeted action to improve water quality at all bathing water classified as poor.
West Cumbria Rivers Trust, which applied for bathing status for Crow Park at Derwentwater, said the classification was a wake-up call.
Jodie Mills, director of West Cumbria Rivers Trust, said: “The classification is deeply concerning, but it underscores the importance of our campaign to push for greater accountability and action at pollution sources in our region.
“Without our efforts to secure bathing water status, this crucial data would not have come to light.”
The trust said improving water quality in Derwentwater and beyond would require collaborative efforts from government agencies, landowners, communities, and industry.
It added: “We are urging national and local leaders to prioritise investment in infrastructure improvements and stricter enforcement of pollution regulations. While the results are a stark reminder of the work still needed, they also mark the beginning of a concerted effort to address the pollution issues at their source.”
Jodie said: “The poor classification for Derwentwater is deeply concerning, but it is also an opportunity to drive lasting change. West Cumbria’s rivers and lakes are vital to our environment, economy, heritage and health, and we will not rest until they are clean, and protected for future generations.”
The trust said it was determined to seek bathing water status for more locations across Cumbria to make sure more water monitoring happens in more rivers and lakes, providing essential data.