Three local beaches each earned an A+ for water quality, and one local beach received a failing D+ grade, according to new data and ratings of Long Island Sound beaches released last week by the Save the Sound/Connecticut Fund for the Environment.

The data can be accessed at: www.SoundHealthExplorer.org. The interactive map shows water quality trends from data collected from health departments in New York City, Westchester County, Connecticut and Long Island. The grades are based on how often in the last five years a beach has failed U.S. Environmental Protection Agency bacterial pollution standards for safe swimming.

Waterford Town Beach and Pleasure Beach, also in Waterford, along with Noank Dock beach, all received A+ grades for having no failing water quality tests in the past five years. Greens Harbor Beach in New London, however, received a D+ grade, based on high levels of bacteria that caused 10 percent of water quality samples to fail to meet public health standards, the nonprofit environmental group said in a news release. Across the Sound, seven beaches received failing D or F grades.

Overall, beach water quality continued on an improvement trend across the Sound. About 83 percent of 324 beaches on the New York and Connecticut sides of the Sound met or surpassed national averages for clean water from 2011 to 2015, up from 80 percent in the previous five years, the organization said.

“We want clean beaches that are healthy for all to enjoy,” said Curt Johnson, executive director of Save the Sound. “Our goal is to engage the public in improving their beaches by putting long-term bacteria data trends at the fingertips. Now everyone around the Sound can understand their local water quality conditions and work to keep their favorite beaches open for swimming.”

Other local beaches, with grades and test results on the Sound Health Explorer site are:

• Soundview in Old Lyme, A, 3 percent of samples failed.

• White Sands in Old Lyme, A, 4 percent of samples failed.

• Rocky Neck State Park in East Lyme, B+, 7 percent of samples failed.

• Hole-in-the-Wall in East Lyme, B+, 6 percent of samples failed.

• McCook Point Park in East Lyme, A, 1 percent of samples failed.

• Ocean Beach Park, New London, A, 3 percent of samples failed.

• Eastern Point, Groton, B+, 5 percent of samples failed.

• Esker Point, Groton, B-, 8 percent of samples failed.