As the hours trickle by, hope that the passengers on board the missing Titanic submersible begins to fade.
But despite the news that the oxygen within OceanGate's Titan has likely run out, the huge search and rescue operation continues.
Teams from the US Coast Guard, Canada, and now, the UK, are working tirelessly to track the tiny pod down and bring its crew to safety.
On board are: British billionaire Hamish Harding; Pakistani businessman Shahzada Dawood and his son Suleman; French explorer Paul-Henri Nargeolet; and OceanGate CEO Stockton Rush.
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At the centre of the rescue mission is underwater bot Victor 6000, which is the only device understood to be capable of delving into such incredible depths to retrieve the sub.
The agile device has been sent down thousands of meters beneath the Atlantic Ocean, where it is being operated remotely by L'Atalante - a vessel up on the surface - via a cable.
It is capable of dropping to 6,000 meters - or around 20,000 feet - and is thought to be the best possible chance of locating and rescuing those on board.
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The Victor 6000 also has powerful arms that can be remotely controlled, and which can cut cables or release stuck vessels.
Olivier Lefort is the head of naval operations at Ifremer, which is a state-run French ocean research institute that is operating the robot.
He said about the operation: "Victor is not capable of lifting the submarine up on its own."
But while he admitted the bot has some significant limitations, he claimed it could help hook the submersible up to another, larger vessel that could pull it to safety.
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"Victor is able to do visual exploration with all the video equipment it has.
"It is also equipped with manipulating arms which could be used to extricate the sub, such as by sectioning cables or things that would be blocking it at the bottom," Lefort added.
"We can work non-stop for up to 72 hours, we don't need to stop at night."
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Despite being unable to locate the Titan yet, the US Coast Guard said today (22 June) that the operation was still active.
Rear Admiral John Mauger said: "This is still an active search and rescue at this point and we’re using the equipment that we have on the bottom right now, the remote-operated vehicles to expand our search capability, and then also to provide rescue capability as well.”
The admiral went on to explain that teams are 'making the most' of good weather conditions to try and make progress with the search, explaining: “We have aircraft still flying overhead looking for any indications of the submersible on the surface
“But our focus right now is on the sub-sea search with the new capabilities that we have brought on line.
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“We have remote-operated vehicles that are working along the path line where the planned dive had taken place for the Titan submersible and we have the ability to both search and rescue.”