At 11:10 p.m. on July 25, 1956, 45 miles south of Nantucket Island, the Italian ocean liner Andrea Doria and the Swedish ocean liner Stockholm collide in a heavy Atlantic fog. Fifty-one passengers and crew were killed in the collision, which ripped a great hole in the broad side of the Italian vessel. Miraculously, all 1,660 survivors on the Andrea Doria were rescued from the severely listing ship before it sunk late the next morning. Both ships were equipped with sophisticated radar systems, and authorities were puzzled as to the cause of the accident.

In the mid-1950s, more than 50 passenger liners steamed between Europe and America, exploiting a postwar boom in transatlantic ocean travel. The lavishly appointed Andrea Doria, put to sea in 1953, was the pride of the Italian line. It was built for luxury, not speed, and boasted extensive safety precautions, such as state-of-the-art radar systems and 11 watertight compartments in its hull. The Stockholm, which went into service in 1948, was a more modest ocean liner, less than half the tonnage and carrying 747 passengers and crew on its fateful voyage. The Andrea Doria held 1,706 passengers and crew in its final journey.

On the night of July 25, 1956, the Stockholm was just beginning its journey home to Sweden from New York, while the Andrea Doria was steaming in the opposite direction. The Italian liner had been in an intermittent fog since midafternoon, but Captain Piero Calami only slightly reduced his speed, relying on his ship’s radar to get him to his destination safely and on schedule. The Stockholm, meanwhile, was directed north of its recommended route by Captain H. Gunnar Nordenson, who risked encountering westbound vessels in the name of reducing travel time. The Stockholm also had radar and expected no difficulty in navigating past approaching vessels. It failed to anticipate, however, that a ship like the Andrea Doria could be hidden until the last few minutes by a fogbank.

At 10:45 p.m., the Stockholm showed up on the Doria‘s radar screens, at a distance of about 17 nautical miles. Soon after, the Italian ship showed up on the Stockholm‘s radar, about 12 miles away. What happened next has been subject to dispute, but it’s likely that the crews of both ships misread their radar sets. Captain Calami then exacerbated a dangerous situation by making a turn to port for an unconventional starboard-to-starboard passing, which he wrongly thought the other ship was attempting. About two miles away from each other, the ship’s lights came into view of each other. Third Officer Johan-Ernst Bogislaus Carstens, commanding the bridge of the Stockholm, then made a conventional turn to starboard.

Less than a mile away, Captain Calami realized he was on a collision course with the Stockholm and turned hard to the left, hoping to race past the bow of the Swedish ship. Both ships were too large and moving too fast to make a quick turn. At 11:10 p.m., the Stockholm‘s sharply angled bow, reinforced for breaking ice, smashed 30 feet into the starboard side of the Andrea Doria. For a moment, the smaller ship was lodged there like a cork in a bottle, but then the opposite momentum of the two ships pulled them apart, and the Stockholm‘s smashed bow screeched down the side of the Doria, showering sparks into the air.

Five crewmen of the Stockholm were killed in the collision. On the Andrea Doria, the carnage was much worse. The bow of the Swedish ship crashed through passenger cabins, and 46 passengers and crew were killed. One man watched as his wife was dragged away forever by the retreating bow of the Stockholm. Fourteen-year-old Linda Morgan was asleep on the Doria when the impact somehow catapulted her out of bed and onto the Stockholm’s crushed bow. She was later dubbed “the miracle girl” by the press.

With seven of its 10 decks open to the Atlantic waters, the Andrea Doria listed more than 20 degrees to port in minutes, and its watertight compartments were compromised. A lifeboat evacuation began on the doomed ship. The evacuation initially went far from smoothly. The port side could not be used because the ship was listing too much, which left 1,044 lifeboat seats for the 1,706 on board. Passengers in the lower cabins fought their way through darkened hallways filling up with ocean water and leaking oil. The first lifeboat was not deployed until an hour after the collision, and it held more crew than passengers.

Fortunately, the Stockholm, which had suffered a nonfatal blow, was able to lend its lifeboats to the evacuation effort. Several ships heard the Doria‘s mayday and came to assist. At 2:00 a.m. on July 26, the Ile de France, another great ocean liner, arrived and took charge of the rescue effort. It was the greatest civilian maritime rescue in history, and 1,660 lives were saved. The Stockholm limped back to New York.

At 10:09 a.m. on July 26, the Andrea Doria sank into the Atlantic. Almost immediately, the wreck, located at a depth of 240 feet of water, became a popular scuba diving destination. However, because of the extreme depth, the presence of sharks, and unpredictable currents, the Doria is known as the “Mount Everest” of diving locations.