The National Resources Defense Council analyzes federal data on beach water. The group said elevated levels of bacterial contamination were found at 11 percent of California's beaches in 2010.
"In California, more than 5,700 closing and advisory days were reported, nearly double the number from 2009," said Noah Garrison of the National Resources Defense Council.
The waters south of the Santa Monica Pier are already known for chemical pollution. But the latest report involves bacterial levels - the germs that can make you sick.
The NRDC says bacteria levels shot up because of heavy rainfall, which sends waste from humans and animals into the ocean.
Among the list of most polluted beaches in Southern California were Avalon Beach, Cabrillo Beach and Colorado Lagoon in Los Angeles County.
In Orange County, Poche Beach and Doheny State Beach also exceeded standards for contaminated water.
Oddly enough, the NRDC says there are some great beaches near the ones that score low, including portions of Hermosa Beach, Manhattan Beach, Dockweiler State Beach, Laguna Beach and Newport Beach.
The report also proposes solutions - methods to capture water and re-use it or paving with permeable asphalt. It allows water to absorb into the soil instead of washing to the beach .
The NRDC says water conservation is key to reversing the trend. Out of 30 coastal states, California ranks 22 for the number of beach water samples that exceeded the national standard.