The ‘Holy Grail of Shipwrecks’ Is Still Underwater. So Is Its $17 Billion Fortune.

Here’s what you’ll learn when you read this story:

• Considered the world’s richest shipwreck, the San Jose was found off the coast of Colombia in 2015.
• New research into the gold coins now scattered on the ocean floor offered insights into the decorative pieces minted in Lima.
• Valued at a modern-day $17 billion, the San Jose’s bounty is still untouched.

Exploration of the San Jose shipwreck and the precious metal coins it scattered about 1,970 feet below the ocean’s surface off the coast of Colombia confirmed it really was the richest shipwreck in the world.

Considered the Holy Grail of all shipwrecks, the Spanish galleon San Jose blew up and sank in 1708 at the hands of British cannons, and it took with it what experts have estimated to be $17 billion in modern-day wealth, largely in the form of coins from 10 years of taxes saved up from the Americas. The shipwreck was first located in 2015.

A new study published in the journal Antiquity showed how using remotely operated vehicles allowed researchers to get close to the underwater coins and confirm that the wreck found in 2015—which launched a custody battle between Colombia and Spain—really is the long-sought San Jose with an untold number of coins still on the seafloor.

“Among the key finds are hand-struck, irregularly shaped coins—known as cobs in English and macuquinas in Spanish—that served as the primary currency in the Americas for more than two centuries,” the study’s lead author, Daniela Vargas Ariza, wrote about the coins often cut from gold or silver ingots. Ariza is a maritime archaeologist at Colombia’s Almirante Padilla Naval Cadet School in Cartagena and the Colombian Institute of Anthropology and History in Bogota.

The exact number of coins visible is difficult to determine due to the nature of the underwater site, but the cobs identified in high-resolution photos taken by the ROV show they have an average diameter of 1.3 inches and weigh 27 grams. At an estimated 200 tons of gold, silver, and uncut gemstones, that’s a lot of wealth in the water.

The photographs did help add some detail to what’s known about the shipwreck’s treasure. One side of the coins featured a Jerusalem Cross—a large cross with four smaller crosses—along with a shield featuring a castle and lions within a dotted border. On the flip side, the central design features the Pillars of Hercules above waves of the sea. The researchers said the design of the waves offers an identifying element for coins coming from the Lima Mint. Coins also feature marks of an assayer—an expert who tests metal purity—hammered on the edges.

The researchers believe the evidence gleaned from the cobs help substantiate the long-held hypothesis that this wreck truly is the San Jose. “This case study highlights the value of coins as key chronological markers in the identification of shipwrecks, particularly those from the Tierra Firme Fleet,” Ariza wrote.

The sinking of the ship at this site must have occurred after 1707, the year the coins were minted. This, along with the presence of Chinese porcelain from the Kangzi period of 1662-1722 A.D. and the inscriptions on the cannon dating to 1665, suggest the ship sank in the early 18^th century.

The features on the coins also helped determine the route taken by the sunken vessel, including how the cobs were likely sourced from Peruvian mines (minting of gold coins began at the Lima Mint in 1696).

There’s also historical context important in identifying the wreck. In 1706, the Viceroy Marques de Castelldosrius arrived in Peru to reactivate the Portobello fair and send accumulated taxes of a decade to the Iberian Peninsula. In late 1707, Peruvian merchants and officials traveled to Puerto Perico on the Pacific coast of Panama, according to the study.

There, they met the Tierra Firme Fleet, commanded by the galleon San Jose, which held the monopoly on transporting royal treasures between South America and the Iberian Peninsula. After the Portobello fair, the San Jose departed for Cartagena carrying goods and metals, including the cobs.

“The San Jose Galleon,” the authors wrote, “is the only ship that matches these characteristics.”

Cobs were the primary way the Spanish transported large volumes of wealth from the Americas to Europe, so these coin hoards likely formed part of the royal treasure dispatched from Peru by Castelldosrius. But when the fleet of 18 ships left Cartagena bound for Spain on June 8, 1708, it was attacked by five British warships during the War of the Spanish Succession. The cannon battle resulted in the exploding of San Jose’s gunpowder stores, sinking the 150-foot-long ship.