A tourist submarine diving to the wreck of the Titanic has gone missing, rescue officials say..The sub was carrying five people when it vanished as it made it's way into nearly four kilometres of water..It has enough oxygen to last 70 to 96 hours..Officials with the Boston coastguard said a search and rescue mission has been launched. They said the sub lost contact with its mothership about one hour 45 minutes into the dive..Coast Guard Rear Adm. John Mauger said both American and Canadian ships are headed to the site. He said aircraft has dropped sonar bouys which has the ability to reach the ocean floor.."It is a challenge to conduct a search in that remote an area," said Mauger, adding nearby commercial vessels have been told to head to the area..He said officials are reaching out the the US Navy, the Canadian Armed Forces and private industry to see what equipment is available for any possible deep sea rescue..The sub is operated by a company called OceanGate, which two years ago started taking small crews of “citizen scientists” in a five-person mini sub for $250,000 per person..“We are exploring and mobilizing all options to bring the crew back safely,” it said on Monday, according to the BBC.“Our entire focus is on the crew members in the submersible and their families.”.“We are working toward the safe return of the crew members,” it added.British billionaire Hamish Harding, chairman of Action Aviation, wrote on Facebook he would be on the missing sub."I am proud to finally announce that I joined OceanGate Expeditions for their RMS TITANIC Mission as a mission specialist on the sub going down to the Titanic," he wrote. "Due to the worst winter in Newfoundland in 40 years, this mission is likely to be the first and only manned mission to the Titanic in 2023. A weather window has just opened up and we are going to attempt a dive tomorrow. We started steaming from St. Johns, Newfoundland, Canada yesterday and are planning to start dive operations around 4 am tomorrow morning. Until then we have a lot of preparations and briefings to do.""The team on the sub has a couple of legendary explorers, some of which have done over 30 dives to the RMS Titanic since the 1980s including PH Nargeolet.". Hamish HardingHamish Harding .The adventurer helped build ice runways in Antarctica, captured the Guinness World Record for circumnavigation of the earth via North and South Poles in a Gulfstream G650ER in 46 hours 40 minutes, dove to the deepest point of the Mariana Trench, the Challenger Deep, in a two-man submarine to the lowest point in the world's oceans to a depth of 36,000 ft., and flew to space onboard New Shepard, as part of the Blue Origin NS-21 mission, on 4 June 2022.The Guardian reported the company’s website had a planned eight-day, seven-night expedition to the wreck planned for 12-20 June. A maximum of six visitors were scheduled to depart and return to St John’s, Newfoundland, Canada..“Follow in Jacques Cousteau’s footsteps and become an underwater explorer — beginning with a dive to the wreck of the RMS Titanic. This is your chance to step outside of everyday life and discover something truly extraordinary,” OceanGate said on its website..“Become one of the few to see the Titanic with your own eyes. Your dive will provide not only a thrilling and unique travel experience, but also help the scientific community learn more about the wreck and the deep ocean environment. Every dive also has a scientific objective and you can learn more about the research we support here.”.The Titanic sank after hitting an iceberg on it's maiden voyage, almost 600 km off the coast of Newfoundland..The shipwreck claimed the lives of 1,514 of the 2,224 passengers and crew.