But the only people on the sand Thursday were Pennsylvania Department of Environmental Protection employees testing for the source of an E. coli outbreak that has sickened at least 11 park-goers.
"I'm glad they closed (the lake) because I wouldn't want other kids getting sick," said Chris Kendle of Smithsburg.
Curt and Chris Kendle traveled with their daughter, Jennifer, and three others to Cowans Gap State Park in Fulton County, Pa., for a few days worth of vacation. They heard about the lake closure as they were leaving their home.
"I would've swam," Jennifer Kendle said. "I'd swim because they don't even know if it's here."
One day of lake testing in mid-July revealed E. coli levels outside the acceptable limits, but they returned to trace levels the next day. All the other regular water tests this summer posted results below acceptable limits.
As a precaution, state officials closed the lake to all activities at 5:30 p.m. Tuesday.
Now, state environmental protection officials are using equipment borrowed from the federal Centers for Disease Control to pump and siphon the area. That equipment allows for testing of the lake's sediment.
Initial testing of the park's sewage system revealed no leaks, according to Terry Brady, spokesman for the Pennsylvania Department of Conservation and Natural Resources, which oversees state parks.
The Pennsylvania Department of Health announced Thursday that the number of confirmed park-related E. coli cases is now 11, with nine cases involving Pennsylvania residents and two involving Maryland residents. Ten of the cases are children.
Richard and Lynn Wyvill made the annual trip to Cowans Gap from their Washington, D.C.-area home Thursday. They saw the "beach is closed" signs, but were unsure why.
"We said, 'Boy, it's quiet today,'" Lynn Wyvill said.
The couple planned to hike the lake's perimeter instead.
Danielle Yohe of Hagerstown was wearing her bathing suit as she despondently watched the environmental protection crews from a picnic table.
"This was my birthday present," said Danielle, who turns 14 today.
"We heard (about the closure) on the news, but we thought it was taken care of," her father, Donald Yohe, said.
The Yohes' family friend, Frank Burns of Huyett, Md., said he hadn't been to the park in several years.
"I used to bring my mom up a lot. ... She just loved the mountains," he said.
Fred and Rose Rupert of York County, Pa., rented a cabin for the week at the same park where they honeymooned.
"To me, this is one of the best places on Earth," Rose Rupert said.
The Ruperts said they encountered a vacant Cowans Gap beach twice before in their years visiting the park — once during a state worker strike and once when the lake was being drained.
On Thursday, the vast majority of campsites at Cowans Gap were empty. Brady said it's difficult to know how much revenue will be lost because of the beach closure.
"There's been a widespread effort by the park system to let the campers know," Brady said, noting that people with site and boat reservations are being contacted about the closure.
There's no way to know when the lake will reopen, he said.