The last time I was at Coney Island beach in Brooklyn, about a few weeks ago, the water was a murky brown and smelled like sewage.

This, however, didn’t seem to faze the kids who were swimming in it or delving into litter-strewn sand. Walking across the beach could produce anything from cigarette butts, to discarded Nathan’s hot dog boxes, to dirty diapers under your bare feet.

Now, it appears that a good chunk of other U.S. beaches are equally dirty — and dangerously so. A new report out of the Natural Resources Defense Council (NRDC) found that 10 percent of U.S. beaches are filled with sewage and other contaminants, at levels way beyond the EPA’s swimmers’ safety threshold. In particular, the report singled out certain areas as the worst offenders — these included New England, the Gulf Coast, the Great Lakes region, and some areas of the West Coast. A good number of these beaches suffered from urban runoff and pollution.

Meanwhile, Delaware, Maryland, and Virginia all scored highest when it came to “superstar” beaches — these states had the most consistently clean beaches over the course of five years, with bacteria levels remaining low throughout this time.

Polluted water at beaches could cause a number of diseases, ranging from skin rashes and pinkeye to stomach flu, dysentery, and hepatitis. According to the EPA, up to 3.5 million people get sick from contact with raw sewage in swimming water every year. “Sewage and contaminated runoff in the water should never ruin a family beach trip,” Jon Devine, a senior attorney at NRDC, said in a statement. “But no matter where you live, urban slobber and other pollution can seriously compromise the water quality at your favorite beach and make your family sick.”

The following beaches have shown “consistent contamination problems,” and are listed on a “repeat offender” list by the NRDC. They have failed to meet public standards for water quality over 25 percent of the time since 2009, so be sure to avoid these:

  • California: Malibu Pier, 50 yards east of the pier, in Los Angeles County
  • Indiana: Jeorse Park Beach in Lake County (both monitored sections): Lake Jeorse Park Beach I, Lake Jeorse Park Beach II.
  • Massachusetts: Cockle Cove Creek in Barnstable County.
  • Maine: Goodies Beach in Knox County.
  • New Jersey: Beachwood Beach in Ocean County.
  • New York: Main Street Beach in Chautauqua County, Wright Park -- East in Chautauqua County, Ontario Beach in Monroe County.
  • Ohio: Lakeshore Park in Ashtabula County, Arcadia Beach in Cuyahoga County, Euclid State Park in Cuyahoga County, Noble Beach in Cuyahoga County, Sims Beach in Cuyahoga County, Villa Angela State Park in Cuyahoga County, Edson Creek in Erie County.
  • Wisconsin: South Shore Beach in Milwaukee County.