Investors who helped bankroll a salvage expedition to recover sunken gold off the coast of Anglesey claim they were misled by the project leader.
Veteran diver Joe McCormack sought the cash after finding what he claimed was evidence of a wrecked galleon intended for Bonnie Prince Charlie in 1746.
But his salvage bid was stopped in late 2009 after running out of money - without unearthing any gold.
Mr McCormack said investors who spoke to the BBC had "an axe to grind".
The BBC's Inside Out North West programme has spoken to 10 investors who funded the ill-fated excavation project who feel they have been misled in some way.
Richard Holland, a doctor of genetics from Southport, put money in and convinced nine other friends and family to do the same, making a total investment of £70,000.
He said: "He [McCormack] was very convincing about the project. It was going to reinvigorate the area around Holyhead. There was going to be a major documentary about the project that we were on and there was going to be a book published as well.
"We've been lied to... not just me, there's a lot of people been told the same story.
"I feel very bitter about it. I feel very embarrassed by it, embarrassed because I've introduced some of my friends into it and I feel bitterly sorry that I've done that and I'm more than angry at Joe McCormack."
After visiting the site near Holyhead last summer, Mr Holland and his friend, Roy McWalters, invested more money to keep it afloat after it ran out of money in September 2009.
Mr McWalters, from Southport - who invested £13,500 - said: "I started to get worried when they were diving and they were bringing up nothing, absolutely nothing."
Mr McCormack's theory is that below the seabed off Holyhead is the wreck of a ship which had been carrying gold from Louis XV of France to Charles Edward Stuart - aka Bonnie Prince Charlie - while he was hiding on the Scottish Islands after the failed Jacobite Rebellion.
Louis XV made attempts to send relief ships to Charlie after he was defeated at the Battle of Culloden, the last of the great Jacobite risings - attempts to reinstate a Stuart monarch on the throne of Britain.
Mr McCormack, from Liverpool, gathered finance for the project after showing investors a ring seal purported to have belonged to Mary Queen of Scots, which he said was recovered by his son on the seabed.
He believes the seal could have been a token of authenticity carried on board to prove they were not British spies.
On his website, Maritime Resurgence, Mr McCormack claims the ring seal was identified by the National Museum of Scotland.
In May 2009, the museum's George Dalglish told the BBC he had authenticated a copper matrix seal, bearing the insignia of Mary Queen of Scots, but did not speculate on its origins.
In a statement, the museum said: "The comments on the Maritime Resurgence website do not set out the full context of our original correspondence with Mr McCormack.
"We do not endorse the content of this website and will be writing to ask that any misleading references to us are removed."
Although the letter from the museum makes it clear the museum had not dated the ring as belonging to the Queen, investors told the programme they still felt misled.
The BBC e-mailed Mr McCormack to inform him of the museum's statement, and in response he conceded the seal's date could not be "100% proven".
But he wrote that, given what was found and where, he still believed it to be original and that it supported his theory that the ring seal was used by the crew of a ship to prove to the Scottish they were allies of Bonnie Prince Charlie.
He added that a small number of investors "had an axe to grind" against him but he declined to be interviewed for the programme.
Inside Out was broadcast on BBC One in the North West on Monday 15 November at 1930 GMT. UK viewers can watch the programme again at www.bbc.co.uk/iplayer.