Tommy Thompson was arrested on a criminal contempt warrant for evading a civil case brought by his investors.
They accuse him of cheating them out of promised proceeds from one of the biggest shipwreck hauls in US history.
In 1988 Thompson recovered millions of dollars' worth of gold from a ship that sank off the US coast in 1857.
Thompson went missing in 2012 amid demands he appear in court. He and an associate, Alison Antekeier, were arrested in January in Boca Raton, Florida.
They had been at the hotel for two years, paying cash for their room under a false name and using taxis and public transport to avoid detection.
The Columbus Dispatch reports that Thompson's plea deal with prosecutors requires him to turn over $425,380 (Â£286,000) to the court, money that was seized when he was arrested.
Under the deal, Thompson will be sent to prison for no more than two years, but in exchange the government will not charge him with other offences arising from the case.
A total of 161 investors had given Mr Thompson $12.7m (Â£8m) to find the ship on the understanding they would see returns on their investment.
Thompson, then an oceanic engineer at Battelle Memorial Institute in Columbus, and his crew brought up thousands of bars and coins in 1988, much of them later sold to a gold marketing group in 2000 for about $50 million.
But the criminal complaint unveiled in January said the gold bars and coins he recovered from the seafloor were worth up to $400m (Â£260m).
One of the investors has asked an Ohio state judge to freeze all of Thompson's assets.
A US treasure hunter - who spent years evading authorities - will go to prison rather than testify about gold he discovered in a historic shipwreck.