This week, researchers announced they’ve found one of history’s most significant—and sought-after—shipwrecks. More than 72 years after it sank in July 1945, the final resting place of USS Indianapolis has been discovered in the Pacific Ocean. But the heavy cruiser isn’t just a cool maritime find; it’s a graveyard. The wreck was the U.S. Navy’s largest-ever single loss of life at sea: an event that left hundreds of sailors dead, hundreds more ambushed by sharks and the American public reeling at the magnitude of a tragedy that took place so close to the end of World War II.

Before it plunged to the bottom of the Pacific Ocean, Indianapolis, named after the capital city of Indiana, played a critical role in the war. In 1941, it narrowly missed the Pearl Harbor attack while participating in military exercises a few hundred miles away. Then, led by Rear Admiral Charles B. McVay III, it supported multiple campaigns throughout the Pacific, including helping provide cover for the Iwo Jima landings in 1945.

But its most famous mission was top secret. As the war hurtled toward its end, Indianapolis was tasked with bringing parts for “Little Boy,” the atomic bomb dropped on Hiroshima, from San Francisco to the Mariana Islands. After completing its mission, and following a quick stop in Guam, the ship was heading toward the Philippines carrying nearly 1,200 sailors—without an escort—when disaster struck on the night of July 30, 1945.

Piece of the USS Indianapolis discovered by the expedition crew of Paul Allen’s research vessel R/V Petrel. (Credit: Paul Allen)

It came in the form of two torpedoes shot from the I-58, a Japanese submarine commanded by Mochitsura Hashimoto. The flaming ship sank in just 12 minutes.

That was just the start of the ordeal for the roughly 900 sailors that survived the initial blast. For days, they floated on parts of the annihilated warship, suffering from starvation and dehydration, their burnt skin blistering in the unforgiving sun. Meanwhile, sharks circled, eating the dead and, eventually, attacking the surviving men—the worst shark attack in history (and an incident famously referenced in the movie Jaws). And help didn’t come, in part because the ship’s distress calls were ignored. Tragically, though U.S. intelligence had intercepted the calls, the military thought they were a Japanese trap and failed to come to the ship’s rescue.

By the time an airplane pilot spotted the wreck three and a half days later, the soldiers that were still alive were hallucinating and near death. A rescue operation was mounted. But it was too late for hundreds of men. Only 317 survived.

“I don’t see this as an average shipwreck,” says David A. Kohnen, director of the John B. Hattendorf Center for Maritime Historical Research at the U.S. Naval College—and not just because of the tragedy. For Kohnen, the wreck doesn’t just stand out because of the loss of life, but because the ship itself was a favorite of the entire U.S. Navy.

Photograph of the USS Indianapolis discovered by the expedition crew of Paul Allen’s research vessel R/V Petrel. (Credit: Paul Allen)

The disaster was a public affairs nightmare for the Navy, says Kohnen, especially since word only leaked to the public after the Japanese surrendered to Allied forces. Stunned by the news of the bombing of Hiroshima and Nagasaki, but happy to see the end of the war, the public could not understand how a tragedy of such magnitude could happen to an American warship so close to war’s end.

Ever since, the wreck has been fodder for historical debates about everything from McVay’s actions to the armed forces’ handling of the disaster to the wreck’s very location. McVay was controversially court-martialed, and blamed for not trying to evade the Japanese torpedoes. Despite the fact that Mochitsura Hashimoto himself testified in his defense, McVay wasn’t exonerated for his role in commanding the doomed ship until 2001, years after his 1968 suicide.

Previously undiscovered information on the potential location of the wreck from a nearby vessel that saw the ship on the day it went down recently came to light, but finding the ship in the 600-square-mile target the search team identified was still the equivalent of finding a needle in an aquatic haystack.

Photograph of the USS Indianapolis discovered by the expedition crew of Paul Allen’s research vessel R/V Petrel. (Credit: Paul Allen)

“There were several challenges we had to overcome during this mission, not least of which was the hostile environment of 5,500 meters and the extreme seafloor terrain,” said Robert Kraft, director of subsea operations and expedition director of Vulcan, Inc ., a civilian company owned by Microsoft co-founder and philanthropist Paul G. Allen, via email. “There is a 2,500-meter-tall mountain range with extreme slopes, peaks and cliffs that put our equipment to the test both physically and technically.”   

It paid off: the crew found the wreck more than 18,000 feet below the surface with the help of their research vessel, the Petrel, and special subsea equipment. Now, at least, there’s one fewer mystery in the tragedy of USS Indianapolis. Though the site is now known to the crew of the Petrel and the U.S. Navy, it will remain confidential and the remains of the ship will be treated as a war grave, in keeping with U.S. law.

“Knowing the location of the wreck provides some level of closure to survivors and a memorial of those that were lost,” Kraft said. “This is an educational opportunity for archaeologists, engineers and historians.” As for Kohnen, he’s glad the wreck will be preserved intact for future generations. “When a ship goes down,” he says, “a little piece of the country goes with it.”