How do we find shipwrecks—and who owns them?

More vessels lie at the bottom of the sea than you might think; the National Oceanic and Atmospheric Administration’s database lists over 10,000 known wrecks off of United States shores alone—and that’s not a complete list. According to United Nations cultural agency UNESCO, there are at least 3 million such wrecks worldwide, some thousands of years old.

(Legendary Spanish galleon shipwreck discovered on Oregon coast.)

And then there’s the booty some of those ships carried. Though there’s an argument to be made that the treasure aboard now-sunken vessels is priceless, some experts estimate as much as $60 billion in precious metals lies on the ocean floor.

But the idea that shipwrecks are there for the discovering—and looting—endangers cultural heritage and vexes authorities and archaeologists alike. And it turns out there’s more to the wrecks than wet wood and centuries-old gold. So what’s behind abandoned, water-bound craft—and how can you help keep them safe? Read on for the truth about shipwrecks.

Why do ships wreck, anyway—and where?

Everything from storms to sabotage can bring a ship down, though it can be difficult to ascertain why exactly a ship sank. Human error is a factor, too: Historically, humans’ ability to build seaworthy vessels and effectively navigate open water was leagues behind the abilities of modern sailors. Even advanced civilizations like ancient Greece faced peril, as in the case of a 2,400-year-old Greek vessel discovered in the Black Sea in 2018—billed as the oldest intact shipwreck ever found.

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Shipwrecks tend to be clustered in areas with perilous conditions or a history of trade or warfare. In the U.S., the Florida coast and the Great Lakes are home to a high concentration of the disasters, with Lake Erie boasting the most wrecks per square mile of any freshwater body on Earth. The Outer Banks of North Carolina earned the nickname “Graveyard of the Atlantic.” International hotspots can be found in places like Bermuda, Greece, the Gulf of Mexico, and the Baltic Sea.

How do people find shipwrecks?

Given the number of shipwrecks, you might think it’s simple to find one. The reality is that most are both inaccessible and unexplored. Professional wreck finders once relied on physical diving and luck to locate shipwrecks. But the ocean can be dangerous and all but impossible to access, especially at non-coastal depths.

But times—and technology—have changed. Researchers now have access to a barrage of sophisticated gear that can help them find long-lost ships. The rising availability of historic documents can point to ships’ final resting places. Remote-sensing techniques like sonar, which uses sound waves, and LiDAR, which uses lasers, allow wreck finders to map the seafloor and underwater objects. And satellite imagery can help pinpoint the plumes of particulate matter generated by wrecks. Scientists are even using artificial intelligence in the search for shipwrecks, with one machine-learning tool proving 92 percent effective at identifying wrecks on imagery taken both above and under water.

(Cursed warship Mars revealed with treasure onboard.)

Once a potential site is located, modern autonomous vehicles can help researchers discover and document wrecks. The robot-like underwater craft can withstand deep waters, locate wrecks, then take photos and video and create maps for researchers above the surface. They can even help assess the chemical composition of the wreckage.

Can I see a shipwreck for myself?

Not always. Even the most high-profile shipwreck finds are often shrouded in secrecy. One of shipwreck history’s greatest finds—that of legendary heavy cruiser U.S.S. Indianapolis—shows why.

(China kept this 800-year-old shipwreck a secret for decades.)

On July 30, 1945, Japanese forces attacked the vessel as its 1,200-man crew headed home from the Mariana Islands (where they had delivered parts of the atomic bomb later used to destroy Hiroshima). Two torpedoes sank the ship in mere minutes, and only 317 men survived—the U.S. Navy’s largest-ever loss at sea.

In 2018, using new information about the attack, a civilian crew scoured a 600-mile area of the remote Pacific Ocean for its remains. They finally located the ship, but its exact location is still a heavily guarded secret to protect both the wreck and the remains of those killed during the attack.

That’s normal for most historic wrecks, which are subject to a variety of protections. However, some are open to the public. Scuba divers can get up close to the abundance 19th and early 20th-century wrecks in Lake Superior’s Isle Royale National Park, and snorkelers off the coast of Florida can view a ship that was part of an 18th-century Spanish flotilla at the San Pedro Underwater Archaeological Preserve State Park. There are also a variety of other underwater museums all over the world. But that doesn’t mean it’s possible to root around for treasure there.

(Here’s where to dive with shipwrecks—and sharks.)

Who owns shipwrecks, anyway?

“People grow up believing it’s finders keepers in the ocean,” says James Goold, an attorney at Covington and Burling, LLP, and a leading lawyer on cases involving the protection of historic shipwrecks.

But in U.S. waters, shipwrecks are subject to strict protections. The 1988 Abandoned Shipwreck Act put states in charge of most shipwrecks found in their waters, and states in turn have their own laws covering wrecks. The Sunken Military Craft Act of 2004 claims national ownership of U.S. military craft that faced watery doom.

Things get trickier when another country lays claim to a wreck. But Goold says that nations have changed the ways they view shipwrecks in recent years—from the “finders keepers” mentality to viewing most wrecks as historic treasures to be shared.

Goold has led a variety of landmark cases that have prompted that shift. In one 2012 case, he represented Spain in a lawsuit involving the wreckage and treasure of the so-called Black Swan, a Spanish frigate sunk by British forces near Portugal in 1804.

“It was the Spanish equivalent of Pearl Harbor,” says Goold. After an American company found the wreck and claimed the booty of nearly a billion dollars’ worth of coins for themselves in 2007, Goold went to court to help Spain assert sovereignty over the ship. Spain won.

“It was a huge moment,” says Goold, who has also represented the National Geographic Society. “It’s Spain’s national history.” And it isn’t just about treasure, he says. “Many people tend to forget these wrecks are often the resting places of people lost at sea.”

Now, in part due to Spain’s efforts to reclaim its lost ships, the international community largely recognizes that a nation’s ship remains its property, even if it sinks in international waters or another nation’s territory and regardless of how long ago the wreck took place.

So what if I find a shipwreck?

If you’re lucky enough to discover a wreck, check yourself. You must contact the local authorities immediately and proceed with your exploration only with a permit. Touching or disturbing the wreck can endanger its research value for archaeologists, ruin fragile remnants, or allow artifacts to fall into the hands of looters or black market merchants.

But the consequences of tampering with a shipwreck may be severe: Treasure hunter and shipwreck hound Tommy Thompson has been imprisoned since 2015 for contempt of court after refusing to tell a federal court where to find a cache of gold coins missing from the 1857 wreck of the S.S. Central America.

Though shipwreck law has tightened in recent years, public perception of shipwrecks as underwater free-for-alls still presents a problem for preservationists. To truly protect the world’s amazing underwater heritage, the public must shift its mentality from treasure-hunting to acknowledging the real value held at the bottom of the ocean: troves of cultural and historical riches.

“These are unique, irreplaceable time capsules,” Goold says. “You can’t just grab souvenirs—those days are over.”