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NEW YORK (CNN) -- Scuba divers got a close look Tuesday at the muck trapping the historic aircraft carrier Intrepid in the Hudson River.
Divers surveyed the Intrepid's hull as they began efforts to determine the amount and composition of the material packed around its stern, rudders and running gear.
The World War II era ship -- now a museum -- got stuck more than a week ago as it began what was to be a trip to a new berth.
In addition to the divers, the Navy was on hand managing a dredging effort, supported by the Army Corps of Engineers.
Crews working Tuesday said they have no idea yet how long the Intrepid will remain stuck.
Bill White, president of the Intrepid Sea, Air & Space Museum, told CNN the recovery effort could take weeks.
A concern is ensuring that dredging around the Intrepid will not pose any health risks, he said.
Museum officials had planned to tow the Intrepid stern-first five miles downriver on November 6 to a shipyard at Bayonne, New Jersey, for restoration and repairs.
It became stuck almost immediately.
Having to abort the move cost close to $1 million. Work for the move included monitoring levels of the Hudson River tides and currents. But all the preparation work proved to be no match for the mud.
The Intrepid, launched in 1943 and decommissioned in 1974, is one of just a few Essex-class carriers still in the water six decades after spearheading the naval defeat of Japan in the Pacific.
In addition to also serving in the Vietnam and Korean wars, it was a recovery ship for NASA astronauts.
Real estate developer Zachary Fisher purchased it in 1981, realizing his dream of turning the ship into the Intrepid Sea, Air & Space Museum a year later.
It has become one of New York's major tourist attractions, drawing some 700,000 visitors a year.
The museum complex also includes a Cold War era diesel-powered submarine, a Concorde supersonic airliner and several historic military aircraft.