A deep sea expert has outlined what the 'worst case scenario' would be for the missing sub that was diving down to the wreckage of the Titanic.
Search and rescue efforts are hoping to track down the OceanGate submersible Titan along with the five people on board before their oxygen runs out tomorrow (22 June).
The US coast guard have said it is a 'complex' rescue operation as they need to first locate the small sub before they try to get it to the surface and rescue those inside.
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Sonar has picked up 'banging noises' near where the vessel went missing which could provide some hope towards locating them but search efforts have been combing '7,600 square miles, an area larger than state of Connecticut'.
Oceanographer and deep sea expert Dr David Gallo said the community 'expected this to happen' at some point.
"We knew darn well it would and we knew all the difficulties around how you recover from it if the sub is stuck on a shipwreck, if they lose batteries and nothing was done about it, there's no policies, there's no plan," he told Sky News about the missing submersible.
"It just frustrates me. Now begins the scramble to try and get the right things at the right place at the right time and it's just an unnecessary step because we did know at some point this was going to happen and I think all of us in the community are stunned.
"It wasn't a surprise in a way, but oh my God it really did happen."
Dr Gallo also explained what the 'worst case scenario' would be in this situation, saying that a 'catastrophic implosion' of the submersible could have happened.
He said: "The worst thing is a collapse - a catastrophic implosion of the sub itself which would be horrific, there's no coming back from that.
"I would have to say that would be the number one option here - which is unpleasant to think about. I don't know how else you can disappear that quickly.
"The ocean does do funny things sometimes, sounds don't go the way they're supposed to go, but sometimes you also have to look at all the evidence and say this is the most obvious route to take, in which case the sub would be very close to where they last heard the pinging from the sub."
Dr Gallo said 'something had to happen midway that caused them to lose power or radio communications'.
Someone who had been on the sub before is Shrenik Baldota, who said on his voyage beneath the sea they got lost for over two hours.
Follow more updates on this story on our live blog here.
Joe Harker