Parks Stephens, the explorer who worked with Titanic director James Cameron, has warned the submersible currently missing and the shipwreck site could be 'a major tragedy'.
'No matter what you may read in the coming hours, all that is truly known at this time is that communications with the submersible have been lost and that is unusual enough to warrant the most serious consideration,' the Titanic expert wrote in a Facebook post on Monday.
'I am most concerned about the souls aboard,' said Stephenson, who has made the journey to the legendary wreck himself.
Stephenson journeyed with Academy Award winning director James Cameron to the 1912 shipwreck while working as the technical advisor to the film that eventually grossed over $2 billion at the box office.
Stephenson has reportedly journeyed to the ocean floor location on several other occasions, including as recently as 2019.
In a further post on Monday, the explorer clarified he would not be conducting interviews on the matter, writing 'I am declining all interview requests. This is an evolving situation and I want to be respectful to everyone who might be affected by what has the potential to be a major tragedy.'
The shipwreck analyst hoped readers would 'keep the well-being of all those potentially affected in your thoughts.'
A massive search operation remains underway to find the missing OceanGate submersible, the Titan, after it lost contact with the mothership during its descent to the shipwreck on Sunday morning.
Rear Admiral John Mauger, who is helping coordinate the search, said it could be stuck.
'We don't have equipment onsite that can do a survey of the bottom,' Mauger said on Tuesday.
'There is a lot of debris, so locating it will be difficult. Right now, we're focused on trying to locate it.'
Royal Navy Rear Admiral Chris Parry likened the bottom of the Atlantic to 'being in space', saying: 'It's utterly dark down there, and you have also got a lot of mud and other stuff getting swept up. You can only see about 20 feet in front of you with searchlights. There are very strong ocean currents which are pushing you along.'
If the mini-sub has lost power, with no working propellers, lights or heating, its five passengers will be in total darkness in temperatures of around 3C (37F) as the doomed craft rolls along the seabed.
Oceanographer and Titanic expert David Gallo said: 'Where is it? Is it on the bottom, is it floating, is it mid-water? That is something that has not been determined yet.
'The water is very deep - two miles plus. It's like a visit to another planet. It is a sunless, cold environment and high pressure.'
The basic problem is that the submersible, Titan, has stopped transmitting signals, making it almost impossible to locate. It is supposed to send a sonar 'ping' (radar and GPS not functioning underwater) to mothership Polar Prince every 15 minutes, but the last one was at 9.45am on Sunday - an hour and 45 minutes into the dive as it was floating right above the Titanic.
For some reason, OceanGate Expeditions, the company that runs the tours of the Titanic, took eight hours to call the coastguard on Sunday. It was reported to the US Coastguard at 5.40pm, and Canada's Coastguard was alerted even later, at 9.13pm.
Among those taking part in the expedition is billionaire Hamish Harding, CEO of Action Aviation in Dubai, and Shahzada Dawood, 48, a UK-based board member of the Prince's Trust charity, and his son Sulaiman Dawood, 19.
The submarine's oxygen supply was estimated at 96 hours, which gives rescue teams until Thursday morning to find the vessel.