PORTLAND (AP) — A treasure hunter who boasted that he’d discovered a sunken British merchant ship containing platinum bars worth $3 billion has put his 220-foot ship up for sale and laid off most of his staff.

Greg Brooks of Sub Sea Research in Gorham, Maine, said the S.S. Port Nicholson, sunk 50 miles off Cape Cod by a German U-boat in 1942 during World War II, carried platinum bars from the Soviet Union that were payment to the U.S. for war supplies. He announced in February 2012: “I’m going to get it, one way or another.”

But some called Brooks’ claims into question from the beginning, and the Portland Press Herald (http://bit.ly/1cC28EX ) reported that the search has come to a halt.

Some investors who bankrolled the salvage effort to the tune of $8 million went to federal court to take over the recovery rights. Meanwhile, Brook’s salvage ship, the Sea Hunter, is listed for sale in Yachting World magazine with an asking price of $2.95 million. Workers have been laid off.

Brooks declined to comment to the newspaper.

This is not the first time the treasure hunter has failed to produce a big payoff, according to the Press Herald. He has been searching waters from Casco Bay to the Caribbean for three decades without success.

Brian Ryder, chief engineer for Brooks for the last 12 years, suggested that Brooks hasn’t given up, saying “boats are always for sale” and that the laid-off workers could be recalled. “It’s a brutal field and there are skeptics everywhere,” he told the newspaper. “You have to believe … and I do.”