On the night of July 25, 1956, the Italian ocean liner SS Andrea Doria was struck by the Swedish ship MS Stockholm in heavy fog off the coast of Nantucket. The collision left the Doria damaged and listing heavily to one side, but thanks to the efforts of rescue ships, 1,660 people were saved before the ship finally capsized and sank the following morning. Fifty-one others lost their lives, igniting a debate over the cause of the disaster that continues to this day.

Though not the largest or fastest ocean liner of its era, the 697-foot Andrea Doria was widely regarded as the most beautiful. Its decks were dotted with three outdoor swimming pools, and it was dubbed a “floating art gallery” for its dazzling array of paintings, tapestries and surrealist murals. There was even a life-sized bronze statue of the ship’s namesake, a 16th century Genoese navigator. Equally impressive were the Doria’s safety features. It boasted two radar screens—a relatively new technology on ocean liners—and its hull was divided into 11 watertight compartments. Anxious travelers could also take solace in the presence of Captain Piero Calamai, a venerable Italian mariner and veteran of both World Wars.

The Doria safely completed 100 transatlantic crossings between 1953 and 1956, and it initially seemed that its 101st would be no different. After leaving Italy on July 17, 1956, the ship stopped at three ports in the Mediterranean and then steamed into the open ocean on a nine-day voyage to New York City. Along with 572 crewmembers, it held 1,134 passengers ranging from Italian immigrant families to business travelers, vacationers and even a few notables such as Hollywood actress Ruth Roman.

Andrea Doria, part of Italy's transatlantic liner fleet, now lies a battered wreck about 300 miles east of New York after colliding with the Swedish liner Stockholm. (Credit: Keystone/Getty Images)
Andrea Doria, part of Italy’s transatlantic liner fleet, now lies a battered wreck about 300 miles east of New York after colliding with the Swedish liner Stockholm. (Credit: Keystone/Getty Images)

On July 25, the Doria entered the heavily trafficked sea-lanes off the Northeast coast of the United States. That same day, the 524-foot Swedish passenger liner Stockholm departed New York on a voyage to its homeport of Gothenburg. By around 10:30 p.m., the two ships were approaching one another from opposite directions off Nantucket. Neither was following the established “rules of the road” for ocean travel. Despite sailing in heavy fog, Captain Calamai had ordered only a minor reduction in speed to stay on schedule for an early morning arrival in New York. Stockholm, meanwhile, was steaming north of the recommended eastbound route in the hope of shaving time off its journey.

Around 10:45 p.m., Calamai’s radar picked up a blip representing Stockholm. The Swedish vessel, under the watch of third officer Johan-Ernst Carstens-Johannsen, spotted the Doria on its own radar a few minutes later. It was a situation both had encountered countless times, yet on this occasion the two ships somehow came to opposite conclusions about one another’s locations. Carstens plotted the Doria to his left and prepared to pass port-to-port, while Calamai, fixing Stockholm’s location to his right, maneuvered for a more unconventional starboard-to-starboard passage. One of the men—it’s still not certain who—had misread his radar and inadvertently steered his ship toward the other.

The officers didn’t realize they were on a collision course until shortly before 11:10 p.m., when Calamai finally spotted Stockholm’s lights through a thick curtain of fog. “She’s coming right at us!” one Doria officer shouted. With just moments to spare, Calamai ordered a hard left turn in an attempt to outrun the other ship. Carstens, having spotted the Doria, tried to reverse his propellers and slow down. It was too late. Stockholm’s icebreaker bow crashed into Andrea Doria’s starboard side like a battering ram, snapping bulkheads and penetrating some 30 feet into its hull. It remained lodged there for a few seconds, then broke loose, leaving a gaping hole in the side of the Doria.

Aerial view of Stockholm entering harbor after crash with Andrea Doria against skyline.  (Credit: Howard Sochurek/The LIFE Picture Collection/Getty Images)
Aerial view of Stockholm entering harbor after crash with Andrea Doria against skyline. (Credit: Howard Sochurek/The LIFE Picture Collection/Getty Images)

Onboard Andrea Doria, passengers felt a tremendous jolt accompanied by the sound of clanging metal. Actress Ruth Roman described hearing a “big explosion like a firecracker.” In one of the lounges, the ship’s orchestra was playing the song “Arrivederci, Roma” when they were abruptly hurled from their stage by the force of the crash.

Those who only ended up with scrapes and bruises could consider themselves fortunate. The collision killed five people on Stockholm and dozens more on the Doria, which had seen a large section of its starboard side turned into twisted metal. Italian immigrant Maria Sergio and her four young children all perished on impact as they slept. In another cabin, Brooklyn resident Walter Carlin discovered that the exterior wall of his room had been completely sheared off. His wife, who had been reading in bed, had simply disappeared. By far the most extraordinary story concerned Linda Morgan, who was sleeping in a starboard side cabin. The crash killed her stepfather and stepsister, but Morgan was somehow lifted from her bed and thrown onto the crumpled bow of Stockholm, where she landed with only a broken arm. “I was on the Andrea Doria,” she told the astonished Stockholm sailor who found her. “Where am I now?”

Following the shock of the collision, both crews scrambled to take stock of their vessels. While Stockholm was found to be in no danger of sinking, the Doria had sustained critical damage and was listing over 20 degrees to its starboard side, allowing seawater to spill through its watertight compartments. Calamai resigned himself to abandoning ship, but soon encountered a catastrophic problem: the list was so bad that the Doria’s eight portside lifeboats could no longer be launched. The remaining starboard side craft could only carry around 1,000 of the ship’s passengers and crew. “Here danger immediate,” Andrea Doria radioed. “Need lifeboats—as many as possible—can’t use our lifeboats.”

Promenade deck of French Liner le de France occupied by survivors of Andrea Doria.  (Credit: Loomis Dean/The LIFE Picture Collection/Getty Images)
Promenade deck of French Liner le de France occupied by survivors of Andrea Doria. (Credit: Loomis Dean/The LIFE Picture Collection/Getty Images)

Luckily for Calamai, his ship was floating in a heavily traveled strip of the Atlantic. While the mangled Stockholm began rescuing passengers from the Doria, several other vessels answered its distress calls and raced to the scene. The first, a small freighter called the Cape Ann, arrived around 12:30 a.m. Two American Navy ships followed shortly thereafter, but lifeboats remained scarce. Finally, around 2 a.m., a massive French ocean liner called the Ile de France maneuvered alongside the Doria, lit up the darkness with its floodlights and began making rescues with its lifeboats.

Though help had arrived, the situation aboard the Doria remained perilous. Debris from the collision had trapped some of the passengers in their cabins, and many on the lower levels had to brave smoke-filled hallways and knee-deep water on their way to the main deck. Those who gathered by the useless portside lifeboats faced their own set of problems. With the Doria listing to its right, its main deck had turned into a steep, slippery slope. To reach the starboard side lifeboats, many had to lie on their backs and slide down the deck, making sure to stop before they careened off the edge and into the water. All the while, the ship continued to roll, threatening to capsize at any moment.

Aerial view of Stockholm entering harbor after crash with Andrea Doria against skyline.  (Credit: Howard Sochurek/The LIFE Picture Collection/Getty Images)
Aerial view of Stockholm entering harbor after crash with Andrea Doria against skyline. (Credit: Howard Sochurek/The LIFE Picture Collection/Getty Images)

The rescue—one of the largest in maritime history—lasted several hours, but by 5:30 a.m., nearly all the Doria’s survivors had been evacuated. 753 people were placed aboard the Ile de France, with the rest scattered aboard Stockholm and four other vessels. Captain Calamai seemed ready to go down with his ship, but reluctantly boarded the last lifeboat after his crew refused to leave him behind. A few hours later, as the rescue fleet steamed toward New York harbor, Andrea Doria finally capsized and flooded. At 10:09 a.m., it disappeared beneath the Atlantic.

All told, 51 people had died as a result of the collision—five on Stockholm and 46 on the Doria. The ships’ owners both blamed the other for the tragedy, but following an out of court settlement, a trial was averted and neither was officially held responsible. In the years since, investigators have used crew depositions and computer simulations to try and recreate the night of the disaster. While there were obvious mistakes from both ships, many researchers now believe that Carstens made the crucial error by misreading his radar and concluding that the Doria was several miles farther away than it actually was. Nevertheless, debate over the cause of the wreck continues even today.

Stockholm was eventually repaired and still sails today under the name Astoria. Andrea Doria, meanwhile, rests in some 240 feet of water in the North Atlantic. It has become a hallowed site among scuba divers, who call it the “Mt. Everest” of diving, but poor visibility and unpredictable currents have ensured that 60-year-old wreck is still claiming lives. Since 1956, at least 16 people have perished while trying to explore its watery grave.