9. Coast Guard Beach, Cape Cod, Massachusetts

Accessible only by bicycle or shuttle bus, Coast Guard Beach in Cape Cod, Massachusetts, has coarse sand that creates steep slopes down to the water's edge.

Swimming is only possible during the summer, when water temperatures hover around 60 to 70 degrees Fahrenheit (15.5 to 21.1 Celsius). At other times visitors can explore the old Coast Guard station atop the bluffs, which offers a sweeping view of the barrier islands and the bay.

Coastal expert Stephen Leatherman, who chose the beach as the ninth best in the U.S. for 2009, said that the overall popularity of beaches in general makes their conservation crucial.

"We're trying to [strike] a delicate balance between making the resource available and preserving the environment," he said.