WASHINGTON -- If you plan on hitting the beach this summer, make sure the water is safe before you dive in.

According to the 17th annual beach water quality report released Tuesday by the Natural Resources Defense Council (NRDC), the water at American beaches was unsafe for swimming a record number of days last year.

Using data just collected from the U.S. Environmental Protection Agency, the report, "Testing the Waters: A Guide to Water Quality at Vacation Beaches," tallied more than 25,000 closings and health advisory days at ocean, bay and Great Lakes beaches in 2006. The number of no-swim days caused by stormwater more than doubled from the year before.

"Vacations are being ruined," said Nancy Stoner, the director of the NRDC's water program. "Families can’t use the beaches in their own communities because they are polluted. Kids are getting sick –- all because of sewage and contaminated runoff from outdated, under-funded treatment systems."

In addition to compiling data on 3,500 U.S. beaches, the report this year takes an especially close look at the nation’s highest risk beaches -– those that are either very popular, very close to pollution sources, or both.

Of those highest risk beaches, Ohio, Indiana, Illinois, Rhode Island, and Minnesota ranked the worst for failing to meet national health standards. This new area of focus is the result of a peer review process NRDC undertook with five professionals from local and state health agencies, academia and the research community.

Aging and poorly-designed sewage and storm water systems hold much of the blame for beach water pollution. The problem was compounded by record rainfall, which added to the strain on already overloaded infrastructure, according to the report.

The authors of the report also said that careless urban sprawl in coastal areas is devouring wetlands and other natural buffers such as dunes and beach grass that would otherwise help filter out dangerous pollution.

"A summer rainstorm should not have to mean that endless amounts of pollution are washed down to the beach, or that sewers will overflow," Stoner said. "We can fix leaky pipes; we can require costal developers to maintain vegetation to absorb rain. The solutions are out there."

Sewage spills and overflows caused 1,301 beach closing and advisory days in 2006, an increase of 402 days from 2005. Elevated bacteria levels from miscellaneous sources, such as boat discharges or wildlife, accounted for 410 closing and advisory days, an increase of 77 days from 2005. In addition, more than 14,000 closing and advisory days were due to unknown sources of pollution.

Not only are the beaches polluted, the way they are tested is also failing the American public, according to NRDC public health and water experts.

The current beach water quality standards are 20 years old and rely on obsolete monitoring methods and outdated science that leave beachgoers vulnerable to a range of waterborne illnesses, the authors said. Risks include gastroenteritis, dysentery, hepatitis, respiratory ailments and other serious health problems. For senior citizens, small children, and people with weak immune systems, the results can be fatal.

"What this report means for families heading to the beach this weekend is that they need to be careful. That means they need to do a little homework," said Stoner. "Call your local public health authority. Ask them if the beachwater is safe for swimming. And there is any doubt, or if the water smells bad or looks dirty, stay out of it."