Storm-agitated waters were already proving dangerous Friday along North Carolina's Outer Banks, where the Coast Guard and local authorities spent hours searching for a 12-year-old boy who disappeared while body-boarding. The boy's mother reported seeing him go underwater off the town of Corolla and the board washing ashore without him. The search was called off at 9 p.m.
Coast Guard spokesman Lt. j.g. Scott Hembrook said the waves in the area weren't that high, only about 4 to 6 feet tall.
"What the storm is doing is creating a particularly strong undertow" that can pull swimmers to the bottom, he said. Undertow is created as water that's crashed onshore rushes back out to sea.
Farther north, the Massachusetts Department of Conservation and Recreation announced that it will close beaches in five communities on Saturday until further notice. The agency also canceled all public ferry service in and around Boston on Saturday, citing potential high seas, strong currents and heavy rain. State authorities urged boaters to have their vessels securely moored by Friday night.
Some coastal residents were looking forward to Danny's effects. In this community 40 miles north of the South Carolina line, surf instructor Dave Houck said the building waves promised to be a weekend treat. He said he usually cancels classes when a tropical storm approaches, but he was on the strand Friday to coach some longtime students.
"This is what surfers love as far as the East Coast is concerned," said Houck, 33, of nearby Wilmington. "We don't want the mess. We just want the swells when the storm stays off shore."
On Friday night, the storm was centered about 300 miles (480 kilometers) south of Cape Hatteras and moving north near 8 mph (13 kph). Forecasters expected the storm to increase its speed through the water and turn toward the north-northeast, passing offshore of the Carolinas early Saturday and offshore of New England later that evening.
A tropical storm watch for the North Carolina coast was in effect Friday as Danny maintained top winds of near 40 mph. Small craft advisories were posted along the South Carolina coast.
On the Outer Banks island of Ocracoke, Anchorage Marina dock master Robert Raborn said the warnings of rough seas prompted the usual stream of weekend boaters crossing the Pamlico Sound to cancel reservations for overnight docking space.
"Pretty much everybody's canceled," said Raborn, 40.
The National Weather Service warned there could be swells as high as 7 feet offshore as the storm passed the area.
As he wheeled out bikes and surfboards at Pleasure Island Rentals on Carolina Beach, Craig McGinnity said if anything the offshore storm could boost weekend traffic from people who enjoy the rough surf. Most North Carolina schools opened for the academic year on Tuesday, so fewer families were planning beach vacations.
"We should see an uptick in business as the storm goes by," McGinnity said. "If they close the beaches, I won't rent out surfboards because I don't want to put people in danger."
Associated Press writer Emery P. Dalesio in Raleigh contributed to this story.