Ocean City ranks among the safest beaches in the United States because of the cleanliness of the water, according to the Natural Resources Defense Council.

The Washington-based environmental group gave Maryland's Atlantic resort a five-star rating for having relatively clean water and testing often enough to provide assurance people won't be swimming in human or animal waste.

"Ocean City actually does well year after year," said Nancy Stoner, do-director of the NRDC's water programs. "It’s got clean water, and it’s well monitored and they let people know there’s a problem there. So that’s great."

Rehoboth and Dewey beaches in Delaware and Virginia Beach garnered four stars in the NRDC's 19th annual report evaluating the water quality at US beaches. Among Maryland's Chesapeake Bay beaches, Sandy Point and Point Lookout also got four stars each. Stoner said those beaches would have ranked higher if they tested more often than once a week.

Overall, Maryland's 71 coastal and bay beaches ranked 8th nationwide for their water quality in the NRDC survey. The group does not evaluate beaches on rivers. Just 2 percent of water samples taken at the state's coastal beaches, on average, showed evidence of contamination with human or animal waste that made them unsafe for swimming.

Nationwide, 7 percent of beach water samples failed government standards. Maryland beaches were closed 61 days last year, down from 243 days the year before. Nationwide, there were 20,000 beach closings or no-swimming advisories because of pollution.

Closings are typically prompted by rainfall washing sewage or animal waste into the water. Swimming in contaminated water can result in stomach upsets, skin rashes or even more serious illnesses. Stoner said last year's nationwide beach water quality was not as bad as it had been in prior years, but said the improvement stemmed from two factors - less rainfall in some regions, and less testing, because government agencies ran short of money.

"Lack of rainfall isn’t a permanent solution," she said.

To see how Maryland's beaches rate, go here.