For decades, the Andrea Doria has lured daring treasure hunters and obsessive thrill seekers to the bottom of the Atlantic Ocean in search of the luxurious ocean liner, which sank off the Massachusetts coast on a foggy night in July  1956.

Forty-six people died after the Andrea Doria collided with another ocean liner, shocking observers who considered the vessel unsinkable and tarnishing the romantic allure of the post-war passenger liners that plied the Atlantic.

Despite having less name recognition than the Titanic or the Vasa, the Italian wreck is now considered by many to be the Mount Everest of underwater exploration, according to CBS News. The ship rests about 60 nautical miles from Nantucket on the border of the continental shelf, where the seabed disappears into the abyss.

The remoteness of the wreck, some divers maintain, only deepens the seductive mystery surrounding it.

"The Andrea Doria stands out as the premier shipwreck in American waters," Stockton Rush, co-founder and chief executive  of a Washington state-based ocean exploration company known as OceanGate, told CBS.

The company is organizing the first manned expedition to the wreck in two decades, according to the AP. Using a  five-man submersible known as  Cyclops I, organizers hope to retrieve high-definition video and 3-D sonar images of the shipwreck, the AP reported.

The ship's popularity can be explained by the money and artifacts that are still on board, as well as the unique time period encapsulated within the ship's wreckage, which sits about 240 feet below the surface, according to CBS.

"The Andrea Doria was the first liner to possess three outdoor swimming pools, one each for first, cabin and tourist class," according to an excerpt from the book "Lost Liners," featured on "Her lines were graceful, her public rooms lavishly decorated and crowded with artworks and her most desirable first-class suites as rarified as any that had come before. She was a superb expression of her time and nationality, a ship that combined 1950s modernity with a keen awareness of Italy's extraordinary artistic heritage."

A vintage reproduction Andrea Doria poster will run you about $13 on Amazon, while an original goes for $2,500 on eBay.

Before it collided with the Stockholm — which tore into Andrea Doria's hull, causing it to slowly tilt on its side before sinking 11 hours later — the ocean liner was considered virtually unsinkable. The ship had been outfitted with the latest navigational equipment, including two sets of radar, and was designed with 11 watertight compartments, according to PBS.

"Her 11 watertight compartments were so constructed that she would remain afloat if any two were breached — more than that her builders could not imagine — and so that she would never take on a list of more than 15 degrees. As an extra safety precaution, her lifeboats could still be launched if the list reached 20 degrees," according to PBS. "Yet the Andrea Doria was destined to become the last great lost ship of a transatlantic passenger era that was about to fade away."

Because it took nearly a half day for the ship to sink, more than 1,600 people on board were rescued, according to the AP.

Like the frigid peak to which it is often compared, the shipwreck is alluring, but fraught with risks for anyone who attempts to reach it.

A total of 16 divers have lost their lives trying to see the shipwreck with their own eyes, CBS reported.

According to the Boston Globe, divers have died in myriad ways, from being "lost in the ship’s collapsing compartments" or falling "prey to faulty equipment." Some divers, the paper notes, have "been stricken by the debilitating decompression sickness known as the bends or collapsed when their hearts simply gave out."

And yet, the Globe adds, the deadly wreck has become "one yardstick by which the world’s best divers measure themselves."

According to the Globe: "Some simply kneel on the historic hull. Others rummage through the wreck in search of mementos — china from the well-appointed cruise liner to take home and frame. And every once in a while, someone gets lucky. In 2010, two divers from New Jersey unearthed the 75-pound bell that once adorned the Doria’s deck."

John Hanzl, diving safety officer at the New England Aquarium, told the paper his dive at the site required five years of preparation.

“For me, it was a challenge,” he said.  “I knew that not everybody could do it. . . . There are a lot of harder wrecks, but the Doria has a cachet.”

“There’s so many things that can go wrong on a dive,” Hanzl added.

As the Globe reported, it only takes four minutes to reach the wreck from the surface. Once divers reach the wreck, though, things can get much more complicated:

"But for all the preparation and advanced equipment, divers have only a few minutes to explore the Doria," the paper reported. "The more time divers spend breathing the specially tailored mix of gases required to survive at such depths, the longer they’ll have to spend making their way painstakingly back to the surface. A typical Doria dive includes only 15 or 16 minutes exploring the wreck before divers must leave."
"During those few minutes, divers affix strobe lights to the mooring line to help find their way back. Some hook lines of their own, wound into reels on their equipment, onto the wreck near the mooring line so they can find their way back when their time in the wreck runs out."
"Some of those who have died got tangled or lost in the wreck. Others have panicked, spit out their mouthpieces, and drowned. But most make their way back to the mooring to start their long, slow ascent."

Joel Perry, OceanGate's marketing director, told the AP that some of the other risks include poor visibility and unpredictable currents.

"A big part of the danger is the depth and the risk of nitrogen narcosis,"  Perry said, a condition that can occur below 100 feet in which too much nitrogen builds up in the blood, causing a level of impaired thinking that is often compared to alcohol intoxication.

The ship's depth means divers are restricted from spending more than 20 minutes on the ocean floor with the wreckage. The Cyclops I, which can hold four crew members and one one pilot, can remain below the surface for hours, according to OceanGate.

During their weeklong mission in early June, the company plans to conduct multiple dives each day. The goal, the AP reported, is not to gather artifacts from the ship  but  to explore and document the ship's deterioration.

"The Andrea Doria is rapidly decaying, and using this technology we can build a 3-D map of the wreck with very high accuracy that scientists can use to compare with future decay," Rush said.

"There's a great scientific need for data on thousands of wrecks all over the world," he added.