(KEY WEST, Fla.) -- Roughly 30 miles off the coast of Key West, Florida, sits a ship called The Dare. Its exact location is a closely guarded secret because, deep below the crystal-clear water, through hundreds of years of sand and shells, the crew believes there is a pile of sunken treasure.
The Dare is owned and operated by the company Mel Fisher's Treasures. It’s part of a fleet of salvage ships that have come to these waters for half a century searching for lost riches from the Nuestra Señora de Atocha, a Spanish galleon loaded with gold, silver and gemstones that sank off the Florida coast in a hurricane in 1622.
Treasure from the four-centuries-old vessel is now scattered across the ocean floor by hundreds of other storms, the company says, in a debris field that stretches tens of miles.
But to The Dare and its crew -- many dressed in tie-dye t-shirts, wearing flip flops and living a kind of seafarer's life that keeps them onboard roughly two weeks at a time -- treasure hunting isn't just a passion. It's a profession.
For decades, the promise of riches has brought divers to the ocean off the coast of the Florida Keys, an area ripe with shipwrecks, where just one dive could make millions of dollars.
For nearly as long, Mel Fisher's has been operating a commercial treasure hunting operation, in which investors pay for the cost of the search and then get a cut of whatever booty is found.
ABC News has found dozens of similar companies that hunt for treasure across the globe from ships that have sunk throughout history.
Vince Trotta, captain of The Dare, has led hundreds of treasure-hunting expeditions. His current crew is a mix of veterans and rookies, whose job it is to dive down deep into holes made by the salvage ship on the ocean floor in search of riches.
Armed with metal detectors, sometimes sifting through the sand by hand, his divers look for the smallest glint of treasure on the ocean floor. Whatever they find -- they’ll be the first person to touch it in 400 years.
But despite meticulously mapping the ocean floor, Mel Fisher’s will be the first to tell you: treasure hunting isn't an exact science.
Gary Randolph, the company's vice president and director of operations, tells ABC News making money is possible, but “you have to be in it for the long haul.”
The company has been recovering emeralds, silver and especially gold coins from the Atocha for decades and even sells some of what they recover from a storefront in downtown Key West. But, Randolph says, according to the ship’s manifest, a fortune of treasure onboard has never been found.
“We’re still looking for another approximately half a billion dollars worth in today’s value of treasure,” Randolph said.
But to some historians and archaeologists, Mel Fisher’s and others like them, aren't fortune seekers or adventurers. Many in the historical community believe they're nothing more than pirates, pilfering sunken ships for their own financial gain.
Paul Johnston, curator of maritime history at the Smithsonian Institution, has been trying to shut down treasure hunters for his entire professional career. He accuses the industry of destroying shipwrecks to get at the gold and even breaking historically significant artifacts in the process.
That’s why most of the world’s prestigious museums, like the Smithsonian, reject items that were discovered by treasure hunters, according to Johnston.
“Treasure hunters don't want to conserve things. It takes too long, and it costs too much money to do it. And so they just want to raise, rinse and retail the findings,” Johnston said.
When pressed by ABC News on that criticism, Mel Fisher's pointed to its efforts to preserve the artifacts it recovers. The company even showcases some artifacts in a private museum.
Onboard The Dare, Trotta showed how items were kept in salt water in a bucket. Each item was individually numbered and tagged and the company says they will eventually be taken to their lab to be cleaned and catalogued.
But several professional archaeologists who spoke to ABC News balked at that explanation. They’re worried the company’s methods of digging through the sand are too aggressive and said the very act of taking an artifact out of the water, without first meticulously studying the area it came from, ruins its historical value.
Many archeologists point to guidance from UNESCO, the United Nations agency charged with the preservation of historic landmarks, that deemed treasure hunting a threat to underwater cultural heritage in a landmark convention two decades ago. Today, UNESCO advises that historical artifacts should not be removed from shipwrecks without professional archeologists.
That criticism hasn’t scared off Jeff Hummel, whose Seattle-based crew represents a new breed of underwater fortune seekers. A former software engineer, Hummel’s organization, the Northwest Shipwreck Alliance, also has investors and is looking for a heap of gold, too.
The group used custom submersible robots to locate the wreck of the S.S. Pacific, which sank in the 1870s, sending millions of gold rush riches to the ocean floor off Washington state.
Inside the shipwreck are perfectly preserved artifacts, Hummel claims. He, too, wants to put them in a museum and says he's working with archeologists on his team to determine how any artifacts should be removed. The gold is just a way to pay the bills, he says.
But some federal authorities don’t see it that way.
There’s been a steady stream of red tape Hummel says he’s had to cut through – designed, he believes, to put a stranglehold around new treasure-hunting operations.
“Look at where our artifacts are going to be treated. Look how the collections are being treated now. We are absolutely not pirates,” Hummel said.
Mel Fisher’s is also used to fighting city hall. Forty years ago, its namesake, Mel Fisher himself, went all the way to the Supreme Court, fighting against the state of Florida for ownership of the Atocha wreck and its riches. He won, and they’ve been pulling up treasure ever since.
But nowadays, every dive is under scrutiny like never before, Randolph says.
Even though the company has drawn criticism, Randolph says, “I think there's more that actually really enjoy what we do, because it's exciting. It's the fun, romance and adventure. As Mel would say, you know, the American dream.”
Johnston, on the other hand, believes the industry will gradually diminish as nations restrict treasure recovery.
But back onboard The Dare, there’s no sign its crew will be stopping the search for the mother lode anytime soon.
When Trotta's divers return to the surface from their first dive of the day, there’s a sense of disappointment – no gold this time, just a few pieces of coral. Onto the next dive.