The Natural Resources Defense Council (NRDC) on Wednesday issued its 22nd annual report on the quality of water at the nation’s beaches, and the news was not great: 2011 saw the third-highest number of beach closings and advisories for unsafe-to-swim-in water in more than two decades.

Ocean City was rated one of the nation’s cleanest beaches. (Judy Rolfe/FOR THE WASHINGTON POST)

Such contamination can cause gastrointestinal illness, ear and respiratory tract infections, fever, rash and other ailments, many of which take days or weeks after exposure to materialize. So, the report notes, people often don’t associate their illness with their having gone swimming. That makes it difficult to accurately assess the number of cases of illness that result from contaminated beach water.

The report includes a tool that lets you look up your favorite beach and learn about its water quality.  It also offers tips for choosing a safe beach on your own. For instance, the report suggests,

•  Look for pipes along the beach that drain storm water runoff from the streets, and don't swim near them.

•  Avoid swimming in coastal water that is cloudy or smells bad.

•  Keep your head out of the water.

•  Avoid swimming for at least 24 hours after heavy rains (which can wash pollution into the water).

Some beaches are far more polluted than others. The report lists the 15 beaches in the nation that have repeatedly had the highest annual number of instances in which tested water samples violated public safety standards. None of the Delaware, Maryland or Virginia beaches make that unsavory list.

On a bright note, Ocean City, Md., and Dewey Beach, Del., are included among the report’s twelve “5-star” beaches for their clean water and sound monitoring and reporting practices.

Have you ever taken ill after taking a dip — and figured that the two were connected?