UPDATED: POLICE now fear the worst for missing man Mark David Moylan, who was last seen a week ago in waters off Gravelly Beach Marina.
Inspector Darren Hopkins, of Northern District Support Services, said if Mr Moylan had fallen into the Tamar River, police were searching for his body.
Police will continue mobile patrols along the foreshore today, while the police vessel will search again tomorrow.
A search and rescue team flew over the Tamar River last night, unable to find any trace of the missing sailor.
The helicopter crew searched at low tide over the Gravelly Beach area for Mr Moylan, 42.
He was last seen between 8pm and 9pm on Saturday, January 25, rowing a small aluminium dinghy from the Gravelly Beach Marina to his vessel.
His boat was moored in the bay directly outside the Gravelly Beach Marina.
Police later found Mr Moylan's dinghy washed up onshore, about four kilometres north of his last known location.
Mr Moylan, who lived on his boat, has not been seen since.
Police divers searched waters in Rose Bay, in the Gravelly Beach area, for several hours yesterday morning, but found no evidence of Mr Moylan.
Mr Moylan is 170 centimetres tall, of slim build, with a tanned complexion and short brown wavy hair.
Police urge anyone who knows the whereabouts of Mr Moylan, or who believe they have found any of his possessions, to call Beaconsfield Police Station on 6383 2002 or Tasmania Police on 131 444.