Thousand Islands State Park samples beaches weekly from June 12 to September 4. When sample results are shared via park staff (by calling each park individually), Lake Ontario Waterkeeper updates Swim Guide.

Recreational public beaches in upstate New York are tested at least once every week typically from mid-June to September. Freshwater beaches in New York are posted when a single sample exceeds 235 E. coli / 100 ml or when the geometric mean of samples collected over a 30-day period exceeds 126 E. coli / 100 ml. Chapter I of the State Sanitary Code Subpart 6-2 includes more criteria for freshwater quality, but most monitoring agencies rely on the E. coli standard.

In the USA, the Environmental Protection Agency has two sets of recommendations for freshwater and marine beaches. A single sample at a freshwater beach should not exceed 235 E. coli / 100 ml of water. A single sample at a marine beach should not exceed 104 Enterococci / 100 ml of water. The geometric mean of 5 samples from a freshwater beach should not exceed 126 E. coli / 100 ml of water. The geometric mean of 5 samples from a marine beach should not exceed 35 Enterococci / 100 ml of water. States may choose to use this standard or they may substitute a standard that is "as protective as" the EPA's recommendation. The Beach Act is the nation's primary beach protection law.