WATCH: Previously unseen footage released showing the first time human eyes caught sight of the wreck of HMS Titanic

​The video, lasting just over one hour and 20 minutes, depicts the hulking carcass of the Belfast-built leviathan lying on the seabed, close to two-and-a-half miles beneath the waves.

The footage had only been online less than 24 hours at time of writing, but had already garnered close to half-a-million views on YouTube.

It has been put online by the Woods Hole Oceanographic Institution, a private research body in Massachusetts, USA.

It describes the video as follows: “This rare, uncut, and unnarrated footage of the wreck of Titanic marks the first time humans set eyes on the ill-fated ship since 1912 and includes many other iconic scenes.

"Captured in July 1986 from cameras on the human-occupied submersible Alvin and the newly built, remotely operated Jason Junior, most of this footage has never been released to the public.”

The wreck is 3.8km (about 2.4 miles) underwater, with the closest land being the island of Newfoundland, Canada, hundreds of miles to the north-west.

When it sank on April 15, 1912, it caused the deaths of the majority of the roughly 2,200 people on board.

Estimates of the dead vary, but Belfast city’s Titanic memorial (beside City Hall) bears the names of 1,512 fatal victims of the disaster.

Among those promoting the release of the undersea footage was James Cameron, the director of the movie Titanic.

Writing on Twitter, he said the video allowed viewers to “join the people who witnessed history”.

In a statement to the media, issued via the Woods Hole institute, he went on to say: “More than a century after the loss of Titanic, the human stories embodied in the great ship continue to resonate.

“Like many, I was transfixed when Alvin and Jason Jr. ventured down to and inside the wreck.

"By releasing this footage, WHOI is helping tell an important part of a story that spans generations and circles the globe.”

The release of the footage coincides with the 25th anniversary and re-release of the blockbuster movie.

The institute has said that “efforts to locate and salvage the Titanic began almost immediately after it sank, but technical limitations as well as the vast expanse of the search area in the North Atlantic made it impossible to locate the wreck”.

The discovery itself was made on September 1, 1985, by a team from the institute led by Dr Robert Ballard, working alongside French wreck-hunters.

Argo, a camera sled that was towed from the research vessel Knorr, captured the first photographs the ship on seabed.

Then in July 1986, nine months after pinpointing where the vessel lay, a team from the institute returned to the wreck site using the three-person submersible Alvin (with Dr Ballard aboard), working alongside unmanned rover Jason Junior.

It was during this dive that the footage which has now been released was filmed.

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