A century has passed since the largest and the most luxurious passenger liner, the RMS Titanic, sank on its maiden voyage after crashing with a huge iceberg mid-Atlantic in 1912.

Over the years, scores of scientists and explorers worldwide have intensely studied the causes of disaster; umpteen number of new theories have been put forward. However, none claims to be concrete and unanimous so far.

The 46,000-ton ocean liner was considered unsinkable but turned out to be the worst maritime disaster of all time. Just before the midnight of April 14, 1912, it collided with an iceberg southeast of Cape Race, five of its major compartments ruptured and the ship sank within a few hours.

It was carrying a total of 2,200 passengers, out of which only 700 (mostly first-class passengers) were saved and over 1,500 lost their lives.

Today it rests nearly 12,500 deep down the sea water, around 370 miles south-southeast of the Newfoundland coast

The Titanic was still a mystery for common people till American filmmaker James Cameron came up with a fictional film on the real-time disaster in 1997. The film received worldwide acclaim, and that's when it caught the attention of more and more researchers, as well as the common people.

Recently, on its 100th anniversary, several artifacts of the RMS Titanic found in underwater expeditions were exhibited and auctioned. Also, a Titanic memorial cruise, made by the same company, retraced the same route in remembrance of the ill-fated ship.

Here are some unseen underwater expedition images released on the occasion of the disaster's 100th anniversary.

Other detailed images of the Titanic - then and now - can be seen here. These rare images were released by the National Geographic last month.

Titanic Underwater Expedition Images
The port bow railing of the Titanic lies in 12,600 feet of water about 400 miles east of Nova Scotia as photographed earlier this month as part of a joint scientific and recovery expedition sponsored by the Discovery Channel and RMS Titantic. Scientists plan to illuminate and then raise the hull section of this legendary ocean liner later this month. Reuters
Titanic Underwater Expedition Images
The port bow railing of the RMS Titanic lies in 12,600 feet of water about 400 miles east of Nova Scotia as photographed August 10, 1996, as part of a joint scientific and recovery expedition sponsored by the Discovery Channel and RMS Titantic. Scientists plan to illuminate and then raise the hull section of this legendary ocean liner later this month. Reuters
Titanic Underwater Expedition Images
Wreckage from the Titanic lies on the bottom of the Atlantic Ocean as viewed by a remotely-operated vehicle August 7, 1998. A spokesman for the Discovery Channel announced August 11 that the RMS Titanic crew, which owns the rights to the ship's salvage, had recovered a 20-ton starboard hull plate about 10 miles from the main wreckage site. The plate, which contains portals and is from the first-class section of the ship, will be crucial in trying to understand how the ship sank. Reuters
Titanic Underwater Expedition Images
This photo shows a chain linking a 13-ton section of the hull of the wreck of the RMS Titanic to diesel lift bags August 25, which wil be used to raise the piece to the surface August 28. Reuters
Titanic Underwater Expedition Images
No criminal charges were being planned in connection with an underwater prank in which two skeletons were placed in the Colorado River, Arizona authorities said. Pictured: Divers from a salvage ship make an ill-fated attempt to pull up a section of the hull of the Titanic. Reuters
Titanic Underwater Expedition Images
A remote-controlled robot recovers a piece of coal from the sunken luxury liner the Titanic in this undated photo. The pieces of coal from the "unsinkable" ship that sunk to the bottom of the Atlantic in 1912 are being offered for sale for $25 from the salvage company RMS Titanic, Inc Reuters
Titanic Underwater Expedition Images
The deep-diving submersible Nautile, operated by the French oceanographic agency IFREMER, is lowered into the Atlantic Ocean August 6, some 400 miles east of Nova Scotia as part of a scientific and recovery expedition sponsored by the Discovery Channel and RMS Titanic. Scientists plan to illuminate and then raise the hull section of this legendary ocean liner later this month. Reuters
Titanic Underwater Expedition Images
Russian miniature submarines Mir-1 and Mir-2 are seen under water in the Atlantic Ocean during the search for the Titanic in 2007. Reuters
Titanic Underwater Expedition Images
A Russian miniature submarine is seen under water in the Atlantic Ocean during the search for the Titanic in this Reuters Television image taken from a television broadcast August 2, 2007. Two Russian submersibles started a dive into the Arctic Ocean on Thursday in a mission to symbolically claim the resource-rich region by planting a flag on the seabed under the North Pole, Russian media reported. Reuters
Titanic Underwater Expedition Images
Maritime historian Claes-Goran Wetterholm of Sweeden examines a two storey piece of the Titanic on display for the first time in Boston, September 10. The piece from the mid-section of Titanic's starboard hull was retrieved off the ocean floor August 10, 1998. Reuters
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