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

Click here for a list of the best and worst beaches

Using data 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 closing and health advisory days at ocean, bay and Great Lakes beaches in 2006. The number of no-swim days caused by storm water more than doubled from the year before.

“Vacations are being ruined," said Nancy Stoner, director of NRDC’s water program, in a news release. "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 Kids are getting sick – all because of sewage and contaminated runoff from outdated, under-funded treatment systems."

Click here to read the whole report

Beaches in Ohio, Indiana, Illinois, Rhode Island, and Minnesota ranked the worst for failing to meet national health standards.

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

Experts estimate that as many as 7 million Americans get sick every year from drinking or swimming in water contaminated with bacteria, viruses or parasites, the NCRD said.

The council said the EPA and state agencies should "tighten and enforce controls on all sources of beach water pollution."