Search and rescue teams trying to track down the missing Titanic submersible heard "banging" sounds as they were searching the area, which suggests it could be on the surface. However, even if it isn't at the bottom of the ocean, those inside still have limited time remaining as the vessel is bolted shut from the outside.
Authorities are focusing their search efforts after "banging" noises were detected with sonar, however the US Coast Guard has warned they "don't know the source" of the banging.
The sounds were picked up by the Canadian P-3 aircraft as underwater operations were underway to try and locate the origin of the noises. The sounds were detected in the search area for the missing submarine, which was carrying five passengers when it lost contact while visiting the Titanic wreck on Sunday, June 18.
Ex-commanding submarine officer Andy Coles said in an exclusive interview with The Mirror that even if the submersible could reach the surface, those inside would not be able to open the hatch as it is bolted shut from the outside. The bolted hatch is effectivelt sealing them inside the deep-sea rescue until external help comes.
Submarine search and rescue expert Frank Owen told BBC News that "banging sounds" detected by floating sonobuoys could suggest the Titan submersible is at the surface.
Speaking at a press conference, Captain Jamie Frederick of the First Coast Guard District said after the sounds were detected "operations were relocated in an attempt to explore the origin of the noises, although the searches have yielded negative results they continue."
It's thought the missing sub has enough oxygen to last until approximately 11am BST on Thursday, June 22 - using the estimate that the craft had a 96 hour oxygen supply when it vanished in the Atlantic off the coast of Newfoundland, Canada.
Ex-commanding officer Andy Coles warned the passengers may have already died from hypothermia or carbon dioxide poisoning, even if they did surface. He told The Mirror: "I don't think the submarine has any means of cleaning out the CO2 and re-circulating the air.
"So they will probably go to sleep way before [so] they don't fully suffocate. The other thing to also consider is 3,800 metres down, it's incredibly cold.
"They've probably not got any power and light. Because if they had power, they would have tried to drive to the surface."
Those on board the missing submersible have been identified as French submersible pilot Paul-Henry Nargeolet, British billionaire explorer Hamish Harding, father and son Shahzada and Sulaiman Dawood, and OceanGate CEO Stockton Rush.
The search for the missing sub has expanded once again, with Captain Frederick confirming it is "now approximately two times the size of Connecticut", and that the "subsurface search is up to two and a half miles deep".
The wreck of the Titanic lies around 3,800m below the ocean's surface - a depth which could prove to be a challenge if, in fact, the sub has not surfaced.
