Originally Published: 20 JUN 23 01:36 ET

Updated: 20 JUN 23 14:55 ET

By Nouran Salahieh and Eric Levenson, CNN

(CNN) — Rescue crews searching for a submersible with five people aboard that went missing while touring the Titanic’s wreckage are keeping a nervous eye on the craft’s dwindling oxygen supply as they navigate choppy waters in a remote area of the North Atlantic Ocean.

The Coast Guard and the Royal Canadian Air Force are deploying more aircraft and vessels to aid in the search for the 21-foot vessel, which began its descent to the bottom of the ocean on Sunday morning – and has just four days of emergency capability.

The international search and rescue operation is “doing everything possible” as part of a “complex search effort” but has so far “not yielded any results,” US Coast Guard Capt. Jamie Frederick told reporters Tuesday.

With an estimated 40 hours of oxygen left, Frederick said, officials do not know whether that’s enough time to rescue those onboard.

“I don’t know the answer to that question,” he said. “What I will tell you is, we will do everything in our power to effect a rescue.”

With weather conditions and visibility were improving Tuesday, Frederick said, the fleet of assets joining the operation include a Canadian pipe-laying vessel with underwater capabilities, along with other vessels and aircraft. He said the “unique” and “challenging” search effort has brought together “our nations’ best experts.”

Additionally, the US is moving military and commercial assets to help, according to the Coast Guard and US Transportation Command.

President Joe Biden is “watching events closely,” National Security Council Coordinator for Strategic Communications John Kirby told reporters Tuesday.

Retired US Admiral and former Chairman of the Joint Chiefs of Staff Mike Mullen told CNN’s Christiane Amanpour on Tuesday the longer the search takes, “the less likely a positive outcome will occur.”

Searchers have taken the mission below sea level after scouring an area of the ocean’s surface about the size of Connecticut, US Coast Guard District 1 Rear Admiral John Mauger said Tuesday morning. “We now have underwater search capability on scene, and so we’re going to be using that to see if we can locate the submersible in the water,” he told CNN.

The search zone covers an area about 900 miles east of Cape Cod, Massachusetts, and 13,000 feet deep, Mauger said Monday afternoon. “It is a challenge to conduct a search in that remote area,” he said in a news briefing. “But we are deploying all available assets to make sure that we can locate the craft and rescue the people onboard.”

The submersible known as “Titan” – roughly the size of a minivan – was carrying one pilot and four “mission specialists” when it lost contact with its mother ship about 1 hour and 45 minutes into its descent to explore the Titanic wreckage, authorities said. It has not been heard from in nearly two days since.

The submersible was operated by OceanGate Expeditions, a company that organizes a journey to the ocean floor for a price of $250,000, according to an archived version of its website. The company advertised the experience as a way “to step outside of everyday life and discover something truly extraordinary.”

The 23,000-pound Titan is made of highly engineered carbon fiber and titanium and is equipped with repurposed everyday items, including a video game controller. The vessel has between 70 and 96 hours of life support, the company’s website states.

The expedition reflects the ongoing fascination with the Titanic’s wreckage more than a century after it hit an iceberg and sank on its maiden voyage, killing over 1,500 people. The journey is also part of the growing business of wealthy adventure tourism, along with the space flights of Blue Origin or the rise of guided tours to Mount Everest.

OceanGate CEO and founder Stockton Rush is among the five onboard, according to a source with knowledge of the mission plan.

The others are British businessman Hamish Harding; Pakistani billionaire Shahzada Dawood and his son Sulaiman Dawood; and French diver Paul-Henri Nargeolet, according to CNN reporting.

OceanGate did not immediately respond to CNN’s request for comment about Rush being aboard.

OceanGate in a statement on Monday said “every step possible is being taken to bring the five crew members back safely. We are deeply grateful for the urgent and extensive assistance we are receiving from multiple government agencies and deep-sea companies as we seek to reestablish contact with the submersible.”

The effort to locate those on board has grown by the day. The Coast Guard is searching with aerial and water surface vessels, and the Canadian Armed Forces is also deploying an aircraft to assist in the search, a spokesperson told CNN.

The Canadian research vessel Polar Prince, which took the submersible to the wreckage site, is assisting search and rescue efforts, a spokesperson for its co-owner Horizon Maritime told CNN.

Still, search and rescue operations at sea are like “searching for a needle in a haystack,” former US Navy diver, retired Capt. Bobbie Scholley, told CNN Monday.

“In this case, they knew exactly the location that they were starting with this submersible so they have good data for where to start the search,” Scholley said. The submersible also is going to make sounds with systems on board that sonar buoys should be able to pick up, she said.

Who is aboard the ship

Officials involved in the search have not publicly named those aboard the submersible, but social media posts and friends and family have identified them.

Action Aviation, an aircraft brokerage based in the United Arab Emirates, in a statement on Tuesday confirmed Harding, its chairman, is on board.

“Both the Harding Family and the team at Action Aviation are very grateful for all the kind messages of concern and support from our friends and colleagues,” the statement said. “We are thankful for the continued efforts of the authorities and companies that have stepped in to aid in the rescue efforts. We put great faith and trust in their expertise.”

Harding has an extensive record of adventures: In 2019 he took part in a flight crew that broke the world record for the fastest circumnavigation of the globe via both poles, and in 2020 he became one of the first people to dive to Challenger Deep in the Pacific Ocean, widely believed to be the deepest point in the world’s oceans.

And last year, he paid an undisclosed sum of money for one of the seats on Blue Origin’s space flight.

The day before the vessel went missing, Harding wrote of the Titanic mission: “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.”

A friend told CNN on Tuesday that Harding is “larger than life.”

“He lives exploration. He is an explorer to the core of his soul,” fellow explorer Jannicke Mikkelsen said. “He has been to the bottom of planet earth in the Mariana Trench … he’s even been in space. We circumnavigated the planet together … the north and south pole, and set the world speed record.”

Nargeolet was scheduled to be on Sunday’s dive with him, Harding said Saturday in a Facebook post:

“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,” Harding wrote, according to CNN news partner CTV News.

A spokesperson for Nargeolet’s family, Mathieu Johann, told CNN Tuesday the missing submariner is a “hero” and said, “I hope that, right to the end, like in the movies, he’ll reappear very quickly to reassure us all.”

“What we’re going through right now is this interminable wait,” Johann said.

Nargeolet is a Titanic expert who has taken the trip every year, completing more than 37 dives to the wreck, according to an archived version of OceanGate Expeditions’ website accessible via the Internet Archive’s Wayback Machine.

“Something we always think about as explorers and scientists … we’ve always known something like this could happen and now it’s happened,” said David Gallo, a colleague of Nargeolet and the senior adviser for Strategic Initiatives at RMS Titanic Inc. “But we’re still pretty much in shock, the community is. I hope it has a good ending.”

Further, Shahzada Dawood and his son Sulaiman Dawood, of Pakistan, “embarked on a journey to visit the remnants of the Titanic in the Atlantic Ocean,” their family said Tuesday in a statement. “As of now, contact has been lost with their submersible craft and there is limited information available,” the family said, adding they’re praying for their loved ones’ safe return.

The incident has left the community of undersea explorers in shock, said David Gallo, who called Nargeolet his “closest colleague. “We’ve always known something like this could happen and now it’s happened … I hope it is a good ending,” Gallo, senior adviser for strategic initiatives at RMS Titanic Inc., told CNN.

Submersible did not resurface as expected

The OceanGate Expeditions trip began with a 400-nautical-mile journey from St. John’s, Newfoundland, to the Titanic wreck site. There, the submersible started its descent Sunday morning before losing contact with the Polar Prince, a converted ice breaker that was its mother ship.

The last communication between the vessel and OceanGate staff at the surface came in at 11:47 a.m. The vessel was expected to resurface at 6:10 p.m. but did not do so, and authorities were notified at 6:35 p.m., according to Polar Prince co-owner Miawpukek Maritime Horizon Services.

Chief Mi’sel Joe of Miawpukek First Nation, the expedition’s support vessel, got a call Sunday alerting him that the submersible was two hours overdue and still hadn’t surfaced and communication with it was lost, he said. At that point, requests for search and rescue had gone out, he said.

“There’s a tremendous amount of concern,” Joe said. “I have anguish that people are going through this. I wish there was more I can do.”

Unlike a submarine, a submersible needs a mother ship to launch it, has fewer power reserves and can’t stay underwater as long.

A mother ship can communicate with a submersible “via text messages which are exchanged via a USBL (ultra-short baseline) acoustic system,” according to OceanGate Expeditions’ archived website. The submersible is required to communicate with the ship every 15 minutes or more frequently, if needed, the site says. That USBL system is the only communications link between the submersible and the surface, it adds.

While Titan is made of carbon fiber and titanium, some parts are decidedly low-tech.

“It is operated … by a gaming controller, what essentially looks like a PlayStation controller,” said CNN correspondent Gabe Cohen, who sat in Titan in 2018 while reporting on OceanGate Expeditions for CNN affiliate KOMO.

Cohen was surprised by how simple some of the craft’s technology seemed, he said Tuesday on “CNN This Morning.”

It’s a “tiny vessel, quite cramped and small,” Cohen said. “You have to sit inside of it, shoes off. It can only fit five people.”

A Titanic dive takes about 10 hours from start to finish, including the two and a half hours it takes to reach the bottom, the website says. The company calls its clients “mission specialists,” who are trained as crew members in a variety of different roles, including communicating with the topside tracking team, taking sonar scans and opening and closing the vessel’s dome, the archived site says.

Clients do not need previous maritime experience to join as mission specialists, it adds.

In case of an emergency, the submersible is equipped with basic emergency medical supplies and pilots have basic first aid training, according to OceanGate Expeditions’ website.

Mother ship crew ‘focused onboard here for our friends’

Everybody is “focused onboard here for our friends,” an expedition participant on the Polar Prince said Monday.

“We have a situation that is now the part of a major Search and Rescue effort, being undertaken by major agencies,” Rory Golden said on Facebook after CNN contacted him. “That is where our focus is right now.”

Ninety-six hours of life support on the vessel is “a short amount of time,” said Scholley, the former US Navy diver, though effective resources are being used in the search.

“The hard part is finding the submersible. And once they find the submersible, there are all sorts of situations of how to get that submersible to the surface, and rescue the crew,” Scholley said.

The Coast Guard’s focus is on locating the vessel, Mauger said.

“If we find this vessel in the water, then we will have to affect some sort of rescue or reaching out to different partners within the US Navy, within the Canadian Armed Forces and within private industry to understand what underwater rescue capability might be available,” he added.

Deep sea-mapping company Magellan, known for their one-of-a-kind deep sea imagery of the Titanic, is trying to get involved in the search and rescue efforts but a key transport issue is holding them back. Magellan Chairman David Thompson told CNN that his team is familiar with the site of the wreck and received written notice from OceanGate Expeditions to mobilize early Monday and help.

However, they need an aircraft with the ability to transport their deep-sea diving equipment from the UK to Canada to launch their operation. Specifically, he said, they would require the use of a C-17 Globemaster III military jet.

“We know the wreck site, we know the location, and the equipment we are trying to get picked up is the equipment we used to do that scanning of the Titanic,” Thompson said.

Thompson said the US Air Force or UK Royal Airforce have not gotten back to Magellan letting them know if or when a plane can be procured for them to use to transport the equipment they need to Canada to embark on rescue efforts.