"The man was apparently having trouble with the throttle," said Capt. Warren Royce of the Clear Spring Volunteer Fire Co. "A witness said the man fell off the boat near the West Virginia side, went down a few times and then didn't come back up."
"A personal flotation device was recovered in the boat," Lynch said. "People need to realize they are only good if you use them."
Emergency personnel established a command post on the Maryland side, where the C&O Canal runs along the river bank between Two Locks off Ashton Road and Four Locks on Dam No. 5 Road.
"The current is very swift in this part of the Potomac," said Bo Miller, a member of the Williamsport Fire Co. dive team.
Miller said the water wasn't murky but the current made the search dangerous and difficult.
Divers were aided during the search by DNR police officers in boats, several fire company boats and a large pontoon boat owned by a Bedington (W.Va.) Fire Co. member who volunteered the use of the vessel through the day.
Washington County Special Operations personnel arrived with a boat Wednesday afternoon.
Food, water and soft drinks were taken to the scene by the Emergency Rehab Unit of Washington County.
"We were down in Fairplay all morning Wednesday on a silo fire and then we were called to come here to supply the searchers with food and drinks," said Les Adelsberger, a Rehab volunteer.
Cpl. Glenn Schultz of the DNR Police said the Potomac in the area where the man disappeared was at a normal level Wednesday.
"It's not particularly treacherous here," Schultz said.
Schultz and several other DNR officers staffed their own boat throughout the day.
A special boat unit from nearby Berkeley County, W.Va., joined in late Wednesday afternoon, employing the talents of a specially-trained dog used in water searches.
A Maryland State Police helicopter hovered over the river for more than two hours, trying to spot the man from the air but to no avail.
Volunteers made several trips into Clear Spring to refill fuel tanks for the boats as the search headed into its sixth hour.