The organization has been assessing water quality at more than 600 beaches on the U.S. west coast and issuing an annual report card since 1991.
Each beach is assigned an A to F grade, with higher grades denoting less risk of becoming ill while swimming at that location, the Los Angeles Times reported.
While most Southern California beaches fared well -- Heal the Bay even gave A+ grades to Hermosa Beach, Cabrillo Beach in San Pedro and the Wedge in Newport Beach -- a few were tagged with F grades, including Doheny Beach in Dana Point, Avalon Beach in Catalina and the beaches next to the piers at Redondo Beach and Malibu, the newspaper said.
Grades are often lower during periods of heavy rain, the report pointed out, but Southern California had rainfall totals well below average last winter with a resultant improvement in water quality.
"Rainstorms greatly increase the amount of urban runoff, the greatest source of bacterial pollution at local beaches," Heal the Bay officials said in a statement.