The report found these beaches had the best and worst water quality in all of Boston

Two beaches in South Boston were safe to swim every day in the summer of 2023, while King’s Beach in Lynn was open to swimmers only half the time, according to a report by the advocacy group Save the Harbor/Save the Bay.

The group announced its 2023 Beach Season Water Quality Report Card at a news conference in Revere Beach attended by U.S. Rep. Katherine Clark of Massachusetts, the No. 2 Democrat in the House, and a number of other local officials. In the report, Save the Harbor/Save the Bay used Department of Conservation and Recreation data to examine water quality at public beaches in Lynn, Nahant, Revere, Winthrop, East Boston, South Boston, Dorchester, Quincy and Hull.

Water quality has deteriorated at each beach in 2023, largely due to last summer’s rainy and wet conditions. The group notes that 2023 was the rainiest summer in the Boston area since 1955. Overall, the beaches received a rating of 85%. compared to 93% a year earlier.

One inch of rain can be enough to wash bacteria accumulated in sewers and storm pipes into the ocean, posing a public health risk. However, Save the Harbor deputy director Kristen Berry said 24 hours later the beaches were generally “as clean as ever” as a result of twice-daily tidal cycles.

Both Pleasure Bay and City Point in South Boston achieved perfect scores in 2023 and each of the past six years. King’s Beach was definitely out of the norm with a rating of 55%, and the next lowest was Tenean Beach in South Boston with a rating of 73%.

The report noted that King’s Beach’s score was a “record low” in the Boston area.

Save the Harbor executive director Chris Mancini called the beach cleanup “a difficult and complex infrastructure challenge.”

Clark, who represents Revere, praised the persistence and resilience of the region’s beaches.

“This resilience was a political choice – the result of transformational investments in the Boston Harbor. Now we must make a different choice: mobilize unprecedented action to safeguard these treasures from the impacts of climate change,” she said in a statement. “That’s why I fight every day to remind us of our share of the historic climate investments we’ve made under President Biden.”

Mancini noted that the system for notifying the public about unsafe beach conditions in the state is imperfect.

Beaches across the state use a posting and marking system to notify the public about high levels of bacteria in the water. However, the technology used to test the waters returns results within 24 hours, which means that by the time they are available, the information is out of date.

Mancini appealed to anyone planning to go to the beach to wait one day to return to the water after significant rainfall.

DCR Commissioner Brian Arrigo, a former mayor of Revere, said the department is committed to ensuring “our Metro Boston beaches continue to be among the cleanest in the country.”

Mancini said he hopes the report “will give people the confidence to get out and enjoy our spectacular state beaches.”