The five men trapped in a submersible that went missing on a sightseeing trip of the Titanic could be using Benadryl to "knock themselves out" so they can conserve oxygen.
The tourist submersible, operated by OceanGate, is controlled by a mothership on the surface but worryingly all contact with the ship was lost around one hour and 45 minutes into the dive.
Hamish Harding, a British billionaire, and father and son Shahzada Dawood, 48, and Sulaiman Dawood, 19, from one of the wealthiest families in Pakistan, were on board the submarine, alongside French explorer Paul-Henri Nargeolet, and OceanGate CEO Stockton Rush.
A massive search and rescue operation is currently underway in the mid-Atlantic after the vessel went missing during a dive to the sunken Titanic shipwreck on Sunday - but time is running out.
They only have enough oxygen to last until around midday tomorrow, and now, Colonel Terry Virts, a friend of Hamish, has shared what techniques they could be using to save the precious resource.
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Speaking on BBC Radio 5 Live this morning, Terry said: "(Staying calm), it's the hardest thing to do. What someone had mentioned to me is that one of the protocols would be for the crew to take basically sleeping medicine, Benadryl, just knock yourself out.
"That slows your heart rate, it reduces oxygen consumption, and then the captain would stay awake and he'd be the guy banging on the walls.
"I'm not sure if that's what they're doing but whatever you can do to stay calm would be very important because it not only helps you stay calm and make smart decisions, which is not easy in a situation like this, but it also allows you to breathe less oxygen which is a key thing, that is the limiting factor as I understand it.
"That's what's determining how many hours of life they have left, is their oxygen consumption."
He added: "What I've been saying is the really good news is that we have not had bad news. They lost comms, that's bad news, but we haven't heard a crushing noise of the hull being crushed or exploding.
"If they really are hearing banging sounds, that means that the crew's alive and conscious and trying to be rescued which is just spectacular news.
"Just because they're alive they still need to find them that's not easy and when they find them they need to figure out why they're stuck and can't go up, and when they figure that out they need to get them out and unstuck.
"There's a lot of questions that still need to be answered. I think with our team of coastguard and navy and Canadian Government and private companies, there's an armada of vessels and aircraft that are out there helping them which is great."
Terry joined Hamish on a world-record-breaking trip where the daring duo circumnavigated the globe via the north and south poles in 2019.
He said that he knows Hamish to be calm and collected, which is what you need in a companion when things go wrong on an expedition.
Terry continued: "I've been describing Hamish as the quintessential British explorer, he's definitely an Englishman, he definitely loves exploration, you know he's a businessman and I think he just does that work to fund his exploration habit.
"He and I did a flying program called One More Orbit. We flew over the north and south pole in a long-range business jet to set a world record circumnavigating the earth, and I was able to make a documentary about it.
"He has been to the bottom of the ocean, the Mariana trench, he flew on Jeff Bezos space tourist rocket last year, he is an explorer, he's a member of the Explorers Club and that is what drives him.
"He wants to go do amazing things. He climbed Mt Kilimanjaro, he likes to do what's difficult, what not many people have done, and hopefully learn something along the way.
"I think it's a very human emotion, not everyone is like it probably most people are not like that, but it's always been a thing for us humans to want to explore.
"He's the person you want to be with. In Hollywood, astronauts and pilots are always yelling and screaming and blah blah turn this, that's not the guy you want to go into space with. That's not the guy you want to fly a mission with.
"He's very calm and that's the kind of person you want in a situation like this. Unfortunately, in that submersible there's nothing they can do, there are almost no controls, you can't go out and fix anything, you can't do a space walk, you literally have to sit there and wait.
"Being patient and doing nothing is not a quality for people who are focussed on doing exploration, and that's something they will have to make sure they do - because if they exercise or move around too much they are going to waste oxygen and that's not what they should be doing right now."
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