The US coastguard has insisted an operation to save five occupants of a <a href="https://www.thenationalnews.com/world/us-news/2023/06/21/banging-noises-inconclusive-as-search-for-titanic-submersible-continues/" target="_blank">submersible</a> diving to the wreck of the <a href="https://www.thenationalnews.com/world/uk-news/2023/06/21/titanic-the-worlds-enduring-fascination-with-the-famous-shipwreck/" target="_blank">Titanic</a> is still a rescue mission, despite passing a crucial 96-hour window for oxygen supply. Experts believe the Titan, which was launched on Sunday morning, had four days of oxygen on board, which would have dwindled by Thursday. However, Guillermo Sohnlein, the co-founder of OceanGate, the company operating the missing submersible, said that the five crew members have "longer than what most people think" in terms of survival. In a statement, Mr Sohnlein, who remains a minority shareholder but is no longer involved with the company, expressed confidence that the crew have been utilising their resources wisely and extending their available time by relaxing as much as possible. "I firmly believe that the time window available for their rescue is longer than what most people think," he said. On Thursday afternoon the US Coastguard said it is evaluating a “debris field” discovered within the search area using a remotely-operated vehicle near the wreckage of the Titanic. The US Coastguard is leading the hunt for the craft. It appeared to rule out banging sounds detected earlier from beneath the waves. When questioned about the noises detected by the sonar buoys dropped into the ocean, Rear Admiral John Mauger revealed initial reports found that it was “ocean background noise”. He said: “We’ve taken that information and shared it with top leading experts from the US Navy and the Canadian Navy, and they’re working on the analysis of that information, they’re continuing to work on the analysis of that information. “The initial reports is that there’s a lot of the sounds that were generated were from background ocean noise, but they continue to … look for all available information there. “What’s important to me, and what’s important as the unified command, is that we’ve continued search in the areas where noise was detected with the ROVs that we have from the time of that detection, so we’re not waiting for this analysis to take action. “The analysis is really helpful to our overall search-and-rescue efforts, but we’re not waiting on it, we’ve moved the remote operated vehicles that we’ve had on site to those areas where noise was detected.” Speaking on Thursday after the 96-hour oxygen supply deadline had passed, Rear Admiral Mauger, the chief co-ordinator of the multinational mission in search of a missing submersible near the Titanic wreck, reaffirmed his unwavering focus on rescuing the five-member crew alive. In a series of TV interviews, he emphasised the significance of accounting for people's will to survive in particularly complex situations. “We continue to find that people's will to live really needs to be accounted for as well. And so, we're continuing to search and proceed with rescue efforts,” he said. Those on board the submersible include three fee-paying passengers: British billionaire <a href="https://www.thenationalnews.com/uae/2023/06/20/titanic-submarine-hamish-harding-is-an-adventurer-who-bravely-explores-the-unknown/">Hamish Harding</a>, 58, who lives in Dubai, as well as Pakistani-born businessman Shahzada Dawood, 48, and his son Suleman, 19, a first-year student at the University of Strathclyde in Glasgow. They are also British citizens. The trip cost $250,000 a person. Pilot Stockton Rush, chief executive of the company leading the expedition, was at the helm, with French submersible pilot Paul-Henry Nargeolet the final person on board. An expert in underwater search told <i>The National </i>no one can definitively say how much oxygen is left. Michael Welham, a marine operations specialist and author, told <i>The National </i>the specific levels have not been published, and the behaviour of the passengers will be crucial. Breathing rates will also have an effect on how quickly the oxygen is used up, as people can breathe faster when they are anxious, he said. “I have been in a very similar situation inside a diving bell, where the scrubbing system for removing carbon dioxide had stopped and you're right down then to breathing very, very shallow. You sit quietly and try not to talk,” he said. Professional operations have a log which details the amount of oxygen available and expectations for battery life. “That log hasn't been made available, even if it exists. So everybody's speculating,” Mr Welham said. Mr Welham said the battery life is another complicating factor in the rescue, as it is required to keep the submersible warm. If the battery has now drained, the heating will also fail, sending temperatures plummeting on board. He said he had one experience where the heating failed while he was in a diving bell. “We were sitting there doing exercises and moving our bodies around to try [and keep warm].” Although the rescue is facing serious challenges, Mr Welham said is some way off becoming a recovery operation. “That decision is a way off yet. At this moment in time. It's a search for it and people are still there. Get the thing to the surface and rescue them,” he added. However, the mission to recover the craft will be challenging, he said. First, rescuers have to locate it. Next, they must lower a cable to wrap around the submersible to bring it up. “You have to get it over what you're going to lift because the ROV can't drag it along the seabed,” said Mr Welham. He said its motors are not powerful enough to manoeuvre the cable, so it needs to be dropped as accurately as possible to land next to the craft. That will be a challenge because the vessel it is being lowered down from will be moving, he said. “If the seas are rough it will be rolling. There might be currents that will actually affect that cable and make it bow a bit. “Then you have got to get on to the deck of the boat to unbolt it to get to the people inside.” The submersible lost communication with tour operators on Sunday while about 700km south of St John’s, Newfoundland, during a voyage to the Titanic shipwreck off the coast of Canada.