This week, searchers announced that the warship had been discovered 5 miles off the coast of Maine and 300 feet beneath the surface of the Atlantic Ocean, in a rocky warren.

A team of eight civilian divers found the wreckage of the ship, which the Navy had initially ruled was destroyed by a boiler explosion. But over five decades later, a historian convinced the Navy that the Eagle 56 was the last U.S. warship sunk by a torpedo from a German submarine.

The searchers grappled with 40-degree water and visibility as low as 5 feet while locating and surveying the wreckage, which is protected under federal law because it is a war grave. Forty-nine of the ship’s 62 crew members were killed.

“When you see a 4-inch deck gun, you know you’re not dealing with a fishing boat,” said Ryan King, a member of the technical dive team that discovered the ship.

The Eagle 56 sank on April 23, 1945, off the coast of Cape Elizabeth while towing a practice target for bombers from the nearby Naval Air Station Brunswick. The ship was part of a class of submarine chasers built by Ford Motor Co. to combat German U-boats in World War I; they saw their first substantial action in World War II.

The German submarine U-853 destroyed the Eagle 56, and less than two weeks later, the Navy sank the submarine near Block Island, Rhode Island. The attack on the Eagle 56 occurred less than a month before Germany surrendered to the Allies. It took about 15 minutes for the warship to sink to the ocean floor after a 300-foot water column shot through the air, said Paul Lawton, a naval historian and lawyer from Warren, Massachusetts, who first pursued the cold case of the Eagle.

“There were known to be almost a dozen U-boats in American waters in the final days of the war,” he said.

Lawton said he had developed an interest in the ship’s disappearance in the 1990s after two firefighters from Brockton, Massachusetts, mentioned that their father had died aboard the Eagle.

“We tracked down three of the 13 survivors who were still alive,” he said, adding that he took sworn statements from each of them in the late 1990s and early 2000s. “We just couldn’t believe how a ship could just disappear.”

Around the same time, Lawton asked Garry Kozak, an expert in the use of side-scan sonar, for his help in the search. Kozak spent five years unsuccessfully combing the waters for the ship’s wreckage. He said it was frustrating because, although there was a wealth of eyewitness accounts from the ship’s survivors and those who saw the explosion from land, the warship had somehow vanished.

“With so many observers,” Kozak said, “you should have had literally an X on the water.”

Kozak’s underwater search company has worked on a number of high-profile recovery operations, including the disappearance of Malaysia Airlines Flight 370 in 2014 and the crash of Swissair Flight 111 off the coast of Nova Scotia in 1998.

In 2011, he went back and took a closer look at a mysterious object in one of the sonar images from his previous search for the Eagle 56. In June 2018, King contacted Kozak, a fellow New Hampshire resident, about resuming the search, and Kozak agreed to give him his charts.

Later that month, divers reached the wreckage for the first time. The blast had ripped apart the bow and the stern. King said the ship’s anti-submarine weapons were still intact.

“You realize you are looking at a rack of 15 to 20 depth charges,” he said. “It’s a sobering thought.”

The divers returned to the site 15 to 20 times in the past year with underwater cameras, chronicling their discovery for a Smithsonian Channel documentary called “Hunt for Eagle 56,” which will be broadcast this fall.

Lawton said he was floored when the divers called to tell him about their discovery.

“This wreck is in extremely dangerous waters,” said Lawton, who is also a diver. “They’re on the level of people who summit Mount Everest without assistance. You’re hanging out there in turbid waters, freezing cold waters. You may not be able to see the back of your outstretched hands. This is not Caribbean diving. It looks like a dead zone. It’s almost pitch black. There’s no natural color.”

Because of the depth, technical divers must make several stops during their ascent from the bottom of the ocean to avoid decompression sickness. The divers have day jobs, King noted, and spend their free time looking for shipwrecks as a team. A former science teacher, King is now a technology coordinator for a school district.

In 2001, the Navy ruled that Eagle 56 had been destroyed by a German torpedo, making survivors and the relatives of the sailors who died eligible to receive Purple Hearts. All 13 survivors from the ship have since died.

“It’s the first time in naval history that a correction of that type was made,” Lawton said.

The wreckage is well beyond the reach of recreational divers, according to King, who emphasized that locating the ship was a team effort.

“I just hope that people treat the wreck with as much respect and care as we have,” he said. “To be able to provide the closure to the families — that has been probably the most rewarding part of this process.”

This article originally appeared in The New York Times.