Gull Lake Park Beach in Gravenhurst is under a swimming advisory.
The Simcoe Muskoka District Health Unit (SMDHU) posted the advisory, located at 405 Brock St., on July 7.
The beach isn’t closed, but signs have been posted warning of the risk posed by going for a swim.
You can still go for a swim at a beach posted with a swimming advisory, but if you do, SMDHU officials say you risk developing minor skin, eye, ear, nose or throat infections or stomach illness.
They say to avoid dunking your head underwater or swallowing water.
The geometric samples collected this week mean the beach was 610 E. coli per 100 millilitres, which is over the provincial standard of 200, according to officials with the Town of Gravenhurst.
There are no other swim advisories in Muskoka as of July 8.
SMDHU tests water samples from public beaches in its medical region between June and Sept. every year.