Most Long Island Sound beaches got grades of A or B from Save the Sound during last year's swimming season

Water quality at beaches along Long Island Sound in Nassau and Suffolk counties improved in 2025, according to grades issued by an environmental nonprofit that monitors the waterway.

"There’s really good news for Long Island," said Peter Linderoth, director of healthy waters and lands for Save the Sound, noting that 81 of the 90 beaches reviewed received a grade of A or B.

Some of those receiving an A+ grade include Sea Cliff Beach, McCabe’s Beach in Southold, Centre Island Bay Beach in Bayville and Hobart Beach Inlet in Northport.

At the bottom of the list were Baiting Hollow Camp with a C-, Bayberry Cove Beach in Setauket with a C. Asharoken Beach and six others received a C+.

"Nine are receiving a C, which is not a fail," he said. "If a beach has received a C or below for multiple years, it rises up in terms of being a priority for potential remediation."

Save the Sound issues a detailed report every two years. In alternate years it releases water quality grades for beaches just before the start of summer swimming season based on data collected by local health departments in the previous year and sent to the U.S. Environmental Protection Agency.

"Receiving A and B grades for our waterways reflects years of investment in water quality, environmental stewardship, and partnerships focused on preserving our beaches, bays, and marine habitats," Oyster Bay Town Supervisor Joseph Saladino said in a statement to Newsday. "Clean waterways are critical to our quality of life, local economy, and the environment."

The county health departments collect multiple water samples throughout the season at each beach. The samples are analyzed for indicators of fecal contamination and bacteria that can cause disease. If samples show amounts beyond the state’s safe swimming criteria, the beach could be put under advisory or even closed until the water quality improves.

Save the Sound combines that data and regional precipitation data to determine the beach’s grade.

The high levels of bacteria can be caused by numerous sources — natural and human-made.

Improperly maintained septic systems and cesspools can leach "high levels of fecal indicator bacteria, which can be carried through the groundwater or stormwater to the coastlines," the group pointed out in its 2025 report.

Linderoth said other sources include leaking sewer pipes, waste from Canada geese or dog owners who don’t pick up after their four-legged friends while walking along the beach.

He said green infrastructure such as rain gardens, green roofs and permeable pavement help reduce stormwater impacts on coastal waters, as do replacing outdated cesspools and septic systems.

By creating a map and other information easily accessible on its soundhealthexplorer.org website, the group says it’s helping get this vital data to the general public.

"People look at these grades and they are more likely to advocate, get involved, have their voices be heard for improvements to water quality," Linderoth said.