A video shows the missing submersible on the surface before it began its journey.
The footage was posted to TikTok, and shows a small platform with the submersible on top.
The vehicle and its five occupants have been missing since 18 June, with oxygen now fast running out in the vessel.
A TikToker posted a video from the deck of a ship, with the misty North Atlantic surrounding her.
The submersible, which must be launched from a larger vessel, can be seen on a platform in the background.
The video was uploaded with the caption: “Watching a submarine go down to the Titanic.”
Each of the five occupants paid some $250,000 to make the journey some 3,800m below the surface to see the wreckage of the Titanic.
They had to sign a waiver accepting that the voyage could result in ‘physical injury, emotional trauma, or death’.
The tours are run by OceanGate, which has come under fire after a 2018 lawsuit resurfaced from a member of staff who claimed he had been sacked after raising safety concerns over the submersible.
OceanGate has denied allegations about the safety of its operations.
A spokesperson for OceanGate said: “OceanGate runs an extremely safe operation. Our full focus right now is getting that submersible located and getting those people brought back safely.”
The submersible, which is called Titan, lost contact with the surface around 435 miles south of St John’s in Newfoundland. It had been descending to view the wreckage of the Titanic.
The video was posted by TikToker @abbijaxxxon, an underwater videographer who shares videos of her life living on a ship in the Atlantic.
The videographer poses for a selfie with the vehicle in the background completely unaware of the mystery that would unfold after the vehicle descended into the depths.
Rescuers in the enormous operation don’t have much time left to locate the lost submersible as there is estimated to be less than an hour of oxygen supply left.
The enormous pressure at the bottom of the ocean could have caused the vessel to implode. There is also the problem of carbon dioxide building up in the cabin, which could be more of a danger than the lack of oxygen.