How to Find Sunken Treasure


Modern treasure hunting isn’t all maps and shovels—it takes science, too.


There are plenty of ships in the sea. According to UNESCO, roughly three million shipwrecks across the globe are just waiting to be found, and at least 100 of them boast potential values that top $50 million. So what’s the best-case scenario? Finding the Flor de la Mar, a Portuguese ship that sank north of Sumatra. The storied treasure includes 60 tons of gold and 200 chests of diamonds, emeralds, rubies, and sapphires worth up to $3 billion.




It may seem like cheating, but most unclaimed treasures are too deep for scuba gear.

In fact, salvage companies invest big bucks in equipment to travel miles below the surface. Odyssey Marine Exploration, one of the world’s premier firms, has spent at least $100 million on the essentials, including its 251-foot flagship, the Odyssey Explorer. The ship’s capable of carrying 60 days’ worth of provisions for its 42 crew members; three tow fish for seabed surveys; and two remotely operated vehicles (ROVs) that can dive to 4,000 meters and beyond.

All that equipment pays off in sweet government contracts. In 2010, the Brits gave Odyssey salvage work, paired with archaeological responsibilities, for the SS Gairsoppa—a WWII merchant ship torpedoed about 300 miles southwest of Galway, Ireland, while carrying at least 219 tons of silver. The water’s extreme depth has protected the sunken treasure for decades (it’s 2.9 miles down, nearly half a mile deeper than the Titanic). But the rising price of precious metals has made salvaging the loot an attractive proposition. Today, the Gairsoppa’s cargo of bullion, ingots, and coins is worth around $270 million.


Unfortunately, you can’t just take the barnacle-crusted money and run. As the folks at Odyssey know, recovery is a lengthy process, made even longer by archaeological requirements. Here’s how a typical salvage works: First, the team dispatches a remote-controlled submersible to survey the wreck and take photos to create a detailed mosaic of the scene. Marine archaeologists then direct a fleet of ROVs to search the ship, recording the distribution of artifacts and cataloging any organisms that now call the ship home. When they begin recovering objects, a computer program maps and determines the precise location of each artifact, using a network of acoustic transponders placed on the ocean floor to triangulate locations. Then comes the fun part.

Like a high-stakes arcade crane, scientists use ROVs to spray away the sediment with gentle water pressure, then suck up the tiny, fragile objects with a low-power vacuum. But that’s just the artifacts. Recovering all that precious bullion poses even more technical challenges. Technicians must pluck individual coins and ingots from rotten wooden storage structures and navigate the remote vehicles past rusted metal containers. Odyssey began work on the Gairsoppa in September 2011, and it’s still picking the ship clean. Once it’s done the Gairsoppa will hold the title of largest marine salvage of precious metals in history.


There’s just one hitch in the plunder recovery biz—sometimes the original owners want their loot back. Odyssey recently had to hand over several hundred million dollars’ worth of gold and silver it had salvaged in 2007 from the Spanish galleon Nuestra Señora de las Mercedes. The Spanish government successfully argued in a U.S. federal court that the treasure still belonged to Spain—although the Spaniards also had to fend off a surprise last-minute claim from Peru, where the metal was mined, refined, and coined. Funny how everyone becomes interested in history when there’s a small mountain of gold coins at stake!

This article originally appeared in mental_floss magazine, available wherever brilliant/lots of magazines are sold. Get a free issue here!