For years he doggedly hunted the cargo of a single treasure-packed galleon, the Nuestra Senora de Atocha, which sank in 1622 near the Florida Keys. When he and his son Kane found the wreck in 1985, they recovered treasure worth $400m and as a result Fisher, his family and his long-suffering investors became millionaires.
In the murky world of treasure hunters, Fisher was a hero, a fixture of Key West who could often be found - wearing a trademark gold doubloon around his neck - in dockside bars, talking long into the night about his undersea adventures. When asked why he had chosen his risky and uncertain trade, he said, "For the fun, the romance and the adventure." While he searched for treasure he liked to repeat hopefully, "Today is the day."
But Fisher's success in discovering treasure in an era when salvage was based on British admiralty law, which held salvagers' work to be in the public interest, did not endear him to environmentalists, historians and archaeologists. Their efforts to persuade US authorities to control the salvage trade eventually produced the 1987 Abandoned Shipwreck Act, which put an end to admiralty law and conveyed the rights to wrecks discovered within three miles of the coastline to the states.
Fisher spent much of his time and money in court, fending off efforts to "take his treasure", as he put it, but the new laws made his business untenable and, by June 1998, of thousands of known wrecks, fewer than 20 were under salvage permit. About half of those were Fisher's.
Mel Fisher was born in 1922, hundreds of miles from the sea, in Gary, Indiana, and was trained as a hydraulic engineer at Alabama University. However, he turned his attention to poultry farming in California, and then went on to open a skindiving shop in Redondo Beach. He began diving for bounty, and, on discovering there was little to be had off the California coast, moved his family to Florida and became a serious treasure hunter.
"What Mel lived on was that American dream and being able to actually fulfil it. He let nothing stand in his way," said Pat Clyne, Fisher's spokesman at the Mel Fisher Maritime Heritage Society Museum in Key West. However, his lust for adventure came at a price. In 1975, his son Dirk drowned hunting treasure inside a ship just days after discovering the first signs of the Atocha wreck. It took the Fisher clan another decade to find the "mother lode" of gold and silver in the Atocha cargo that would be their greatest find.
Fisher never strayed far from controversy. Last month he admitted selling counterfeit gold coins at his gift shop in Key West, and agreed to repay to purchasers the prices of the coins - from $2,500 to $10,000 - which had been sold on the understanding that they were from a 1733 Spanish fleet that went aground off the Keys. In a negotiated plea, Fisher pledged that his company would sell only coins recovered from shipwrecks to which it had salvage rights.
Mel Fisher, treasure hunter: born Gary, Indiana 1922; married (three sons, one daughter, and one son deceased); died Key West, Florida 19 December 1998.