The initial incident in 2012, when the cruise ship ran aground in Italy, off a small Tuscan island, with the deaths of 32 people, must have been the most public shipwreck in history. Its subsequent salvage this year, when the 16-story cruise liner was refloated with the aid of 30 huge stabilizing containers and towed to the port of Genoa at an estimated cost of $1 billion could well have been the most expensive recovery of a vessel since men first took to the seas.

By expending so much money and effort to recover the stricken vessel and whatever remains usable aboard, the owners and salvage company have underlined what is coming to be a new maritime truth – that whatever the sea has claimed, it may now have to give up.

Riches brought up from under the seas

In a technical sense, saving the Concordia was not so difficult. But specialists recovery companies are going much deeper, sending down remote survey vehicles and seeking out fabled lost treasures far under the waves. They have already brought some fabulous hoards, lost for hundreds of years and previously way beyond reach, to the surface. And it’s likely that new techniques and improving surveillance technology will enable them to bring up treasures once believed to have been lost forever.

There is no serious talk at present of lifting the Titanic, surely the most famous of all shipwrecked vessels, discovered by an American-French expedition in 1985, to the surface. But there is a flourishing mini-industry based around the display of its recovered contents. Numerous expeditions collected 5,500 artefacts. They have gone on display throughout the world in the “Titanic: The Artefact Exhibition”. In 2007 their sales value at auction was estimated at $200 million.

There are so many ships under the sea. UNESCO put the figure at around three million shipwrecks across the globe, just waiting to be found. At least 100 of them could contain cargoes worth $50 million each, or more.

Sunken ship wrecks around the coast of Britain

One of the first big headline recoveries from under the sea was the Mary Rose, raised gently to the surface, on live TV, in the Solent off Southampton in 1982. Henry VIII’s brand-new flagship, which sank on its maiden voyage, is now a spectacular public exhibit in its own purpose-built quarters.

There are sunken wrecks all around the coast of Britain, often very close to shore. Some places were especially notorious, before the days of guiding lights and maritime charts. Stand on the cliffs at the Gara Rock Hotel east of Salcombe, in Devon, and you may easily see the site of what the British Museum calls “a unique find in the history of Britain”.

One stormy day in the 1600s a galleon sank here, one of many to perish on treacherous rocks over the centuries. In the 1990s divers brought up the “Treasure of the Salcombe Cannon Site”, a fabulous hoard of gold, jewellery, pottery and 400 gold coins, struck by the Sharifs of the Sa’dian dynasty, rulers of Morocco. The BM, which now owns the treasure, sees it as tangible evidence of a flourishing trade between North Africa and Europe from the 16th century.

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The Mediterranean treasures

Those riches came from shallow coastal waters. The quiet, and relatively shallow Mediterranean too, has yielded rich prizes. The Museum of Underwater Archaeology in Bodrum in Turkey displays wondrous riches recovered from the seabed from 3000 years of shipwrecks in coastal waters. Among them is the 14th century BC Kaṣ-Uluburun shipwreck, found in 1982, 120 feet down, with enough metal to make weapons for an entire army.

Another remarkable discovery came in 1976 when a team recovered the Antikythera “mechanism” from the ship of that name. This strange device has been described as the first analogue computer.

One remarkable recent find didn’t even require its discoverers to get their feet wet. Geologists found the “Diamond Shipwreck” buried deep in the sand on the Sperrgebiet beach in Namibia. Archaeologists recovered ingots, cannons, swords, elephant tusks, and thousands of gold coins. They believe this was a Portuguese ship, the Bom Jesus, lost in 1533.

In the late 20th century archaeologists such as Margaret Rule who directed the Mary Rose programme and freelance treasure hunters played a big part in discovering wrecks and recovering their cargoes. The Nuestra Senora de Atocha was one of the great discoveries from that time. It sank, apparently too heavily burdened with riches – gold, copper, silver, indigo, and jewels – off the Florida Keys in 1622. It was located by modern-day treasure hunter Mel Fisher after a 17 year search in 1985. The wreck is still being explored and excavated.

Whydah Gally was the pirate ship of Captain “Black Sam” Bellamy. discovered in 1984 by Barry Clifford, after years of searching. Its treasures are still being recovered today. So far, more than 200,000 artefacts, including gold, jewellery and coins have been brought to the surface. The items travel the world in the exhibition “Real Pirates.”

The Odyssey Marine Exploration’s successes

However the days of the individual treasure hunters, the Indiana Joneses of the sea, may be numbered, as specialist, well-resourced search and recovery companies send their vessels, bristling with technology, out into ever deeper waters.

Odyssey Marine Exploration Is one of a very small number of specialist companies with the budgets and expertise to use the new game-changing technologies to the full. At their disposal are advanced tethered robots that can dive to 4,000 meters and beyond, and lights and claws capable of withstanding the devastating, crushing pressures of the deep.

One important advance is the plastic cable, Dyneema, said to be the world’s strongest fibre, replacing the conventional steel cable which might break under the strain of its weight. The whole undersea operation is controlled with intricate electronic precision. From miles away, technicians can pick up individual coins and ingots from rotten wooden chests, and squeeze them through a tangle of metal in a ship’s interior to the surface.

One of Odyssey’s early successes came in 2004, when the company discovered the SS Republic, a ship lost in 1865 off the US coast. It recovered more than 50,000 coins, worth more than £40m. In 2007 Odyssey raised 16 tons of treasure worth an estimated $500 million from the Spanish galleon Nuestra Señora de las Mercedes, which sank off Portugal’s Atlantic coast. However the Spanish government successfully argued in a U.S. federal court that the treasure still belonged to Spain.

One of its biggest successes came in 2012, when it located the British vessel Gairsoppa, torpedoed 300 miles SW of Ireland by a German U-boat in 1941. It sank, with the loss of all but one of its 86-man crew and lies 2.9 miles down.

In 2012, contracted by the British government, the company sent out its search vessel Odyssey Explorer, which used a tethered robot, taking three and a half hours to reach the seabed, to recover 1,203 silver bars. The UK took the silver back, but Odyssey was well rewarded. To date, this is the heaviest and deepest cargo of precious metal yet lifted from a shipwreck. And there’s more to come, with yet more silver believed to be aboard the Gairsoppa.

The Modern-day treasure hunt process

Once treasure hunters relied on some ancient, often ambiguous, map on a scrap of parchment as they hunted for their prize, and, at least in fiction, many were driven mad in the process. Today the search is likely to begin in a public library and lead through close study of shipping records and maritime charts to a request for permission to search in the offices of whichever government controls the waters where the wreck is believed to lie.

Seafarer Exploration Corporation is a good example of the modern prospecting company, focused on “archaeologically sensitive exploration, research and recovery of historic shipwrecks”, engaged in a painstaking research that might, or might not lead to riches.

In August 2014 Seafarer announced that their first dive at a newly permitted shipwreck site near Cape Canaveral had already yielded “some very exciting artefacts”. The site is believed to contain the remnants of a ship from the early colonial era (1500-1700). Objects retrieved during the first dive appear to reinforce that notion. Divers brought up what appears to be a colonial era cannon 2.46 meters long and 40 centimeters at its widest point. It would have been used to protect the ship and its contents.

The risks of the treasure hunting business

Even when the finds are safely ashore, there is no guarantee that the discoverers get to keep their share. Take the case of the SS Central America, which sank 160 miles off the South Carolina coast in 1857. In a recovery operation in 1987, US firm Columbus-America Discovery Group landed $40 million in gold. Then the litigation started, with an alliance of American and British companies that had insured the steamship’s cargo 135 years earlier claiming rights to the treasure. “One hundred percent of every dime that came in from the sale of the treasure to was used to settle the lawsuits”, said one investor.

The world’s biggest treasures

What still lies beneath the waves? Untold riches. One target is the British warship HMS Sussex, which sank in the Straits of Gibraltar in 1694. The nine tons of gold bullion still thought to be inside would be worth around £2.5billion, most of which would go to the UK Treasury.

Perhaps the most fabulous treasure of all awaiting recovery is on the Flor de la Mar, a Portuguese vessel which sank somewhere north of Sumatra, exact whereabouts still uncertain, in the 1500s. It is said to have been carrying 60 tons of gold and 200 chests of diamonds, emeralds, rubies, and sapphires worth, at today’s prices, as much as $3 billion.

The success that Odyssey has enjoyed makes the company confident that there are more big discoveries to come. A spokesman for the company said he believed the value of cargoes, hitherto thought to be unrecoverable but now within reach, could amount to billions of dollars. Today’s technology and equipment, he said, opens up the entire ocean floor.

He believes marine technologies have improved to the point that no sunken ship is too deep and no cargo too large to be recovered.