The civilian submersible now missing while diving to the Titanic wreck may have suffered a catastrophic leak, an electrical fire, a power blackout or even been swept up in a tremendously powerful underwater current, an expert shipbuilding engineer claims.

Associate Professor Eric Fusil, the director of University of Adelaide's shipbuilding hub, laid out four frightening scenarios that could have caused a loss of communication between the sub and an expedition vessel called the Polar Prince.

The stakes are incredibly high, given the huge challenge of going so deep in the ocean. 

READ MORE: What we know about the missing OceanGate sub and its expedition

"The clock is ticking," Fusil said, as US and Canadian desperately scoured the ocean's surface about 1450km east of Cape Cod and used sonar to listen for sounds far below the water, which is almost 4km deep in the area.

Any submariner knows how unforgiving the abyssal domain is, Fusil said, referring to the depth of water known as the abyssal, or the abyss, ranging from 3000 to 6500 metres.

"Going undersea is as, if not more, challenging than going into space from an engineering perspective," Fusil said.

Though yet to be confirmed, the missing submersible is likely to be the Titan, the only one of OceanGate's three submersibles capable of reaching the Titanic wreckage.

The six-metre vessel has four days of emergency capability and is carrying five people, including British billionaire, Hamish Harding.

According to Fusil, four major risks could have caused a loss of communication on Titan.

Power blackout

The Titan runs on batteries and a loss of power would means loss of communications, Fusil said.

It is unclear if power back-ups (Uninterrupted Power Supplies) are on the Titan at this point in time.

This is why, Fusil said, some submersibles have two independent sources of energy (electrical and other such as compressed air or hydraulic) to power safety systems.

Fire

An electrical fire originating from a short circuit would cause a fire onboard.

On top of ruining the submarine systems, Fusil said the immediate danger is toxic fumes that would poison the atmosphere and intoxicate the passengers, potentially incapacitating them.

If passengers have have access to Built-In Breathing Systems, a kind of oxygen mask, that may help avert complete disaster, he said.

Flood

Submersibles face increasing pressure the deeper they dive.

At 4000 metres, the equivalent of more than 4000 tonne will be applied on an area of 1 square metre.

Titan has a composite hull with inbuilt sensors that can withstand such pressure, but it requires a very accurate round shape.

Fusil said any out of circularity defect could result in a "near instantaneous implosion", occurring at a rate of less than 40 milliseconds, at such depths.

Should some system failure cause the Titan to start to sink, systems such as safety leads, if fitted on the submersible, can be dropped to gain instant lightening and raise to the surface, he said.

"It is a long climb though," he said.

Entangling

Strong currents can occur undersea, and submersibles stay away from anything that could entangle them and block them.

A wreck, such as the Titanic, can present tricky spots if coming too close, where the Titan could get trapped and struggle to free herself, Fusil explained.

Timeline: How the expedition unfolded

Friday, June 16

• Polar Prince departs St John's, Newfoundland, with submersible Titan on board

Sunday, June 18

• Polar Prince reaches the submersible launch site
• One hour and 45 minutes later communications with Titan are lost
• Vessel reported overdue at 9.13pm local time (12.13pm Monday AEST)
• Rescue mission is launched involving US and Canadian coast guards

Monday, June 19

• Rear Admiral John Mauger of the US Coast Guard says the submersible has between 70 and 96 hours of oxygen left
• It's confirmed the submersible had the full complement of five people on board, including UK billionaire Hamish Harding

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The air search for a submersible missing in the Atlantic Ocean as it carried people to view the wreckage of the Titanic will halt overnight, but efforts to discover the vessel's fate won't stop completely.

The Joint Rescue Coordination Centre in Halifax, Canada, said the vessel was reported overdue at 9.13pm on Sunday (12.13pm Monday AEST), about 700 kilometres south of St John's, Newfoundland.

The surface lost communication with the sub one hour and 45 minutes into its journey.

READ MORE: What we know about the missing OceanGate sub and its expedition

Lieutenant Commander Len Hickey said a Canadian Coast Guard vessel and military aircraft were assisting the search effort, which was being led by the US Coast Guard in Boston.

The Polar Prince, the ship which carried the submersible to its dive point, will continue to do surface searches throughout the evening and Canadian P8 Poseidon aircraft will resume their surface and subsurface search in the morning, the Coast Guard said on Twitter.

Alistair Greig, a professor of marine engineering at University College London, warned of the challenges rescuers would face.

He said submersibles typically have a drop weight, which is "a mass they can release in the case of an emergency to bring them up to the surface using buoyancy".

"If there was a power failure and/or communication failure, this might have happened, and the submersible would then be bobbing about on the surface waiting to be found," Greig said.

READ MORE: What could have gone wrong with missing submersible?

Another scenario is a leak in the pressure hull, in which case the prognosis is not good, he said.

"If it has gone down to the seabed and can't get back up under its own power, options are very limited," Greig said.

"While the submersible might still be intact, if it is beyond the continental shelf, there are very few vessels that can get that deep, and certainly not divers."

Even if they could go that deep, he doubts they could attach to the hatch of the submersible.

READ MORE: Man with disability dies after being detained at train station

OceanGate Expeditions confirmed the search for its five-person submersible and said its focus was on those aboard the vessel and their families.

"We are exploring and mobilising all options to bring the crew back safely," the company said in a statement to BBC News.

"Our entire focus is on the crewmembers in the submersible and their families."

David Concannon, an adviser to the company, said Oceangate lost contact with the sub on Sunday morning.

It had a 96-hour oxygen supply, he said in an email to The Associated Press on Monday afternoon (early Tuesday AEST).

"Now 32 hours since sub left surface," said Concannon, who said he was supposed to be on the dive but could not go due to another client matter. 

On Monday night (just before 7am Tuesday AEST) US Coast Guard Rear Admiral John Mauger said the organisation anticipated there was "somewhere between 70 to the full 96 hours" of oxygen available on the vessel.

He said the search for the missing submersible was complex as authorities were searching both underwater and on the surface of the ocean in a very remote location.

Mauger, who confirmed there were five people on board, noting the vessel could have surfaced but might have lost communication with the tour vessel from which it launched.

OceanGate's expeditions to the Titanic wreck site include archaeologists and marine biologists.

The company also brings people who pay to come along, known as "mission specialists."

They take turns operating sonar equipment and performing other tasks in the five-person submersible.

The Coast Guard said Monday that there was one pilot and four "mission specialists" aboard.

C-130 aircraft were searching the surface and two P-8 planes that use sonar to find submarines were part of the search efforts, Mauger said.

Commercial ships are also involved and one has sonar, he added.

"Oftentimes, we rely on commercial operators to be the first vessels on scene," Mauger said.

"And so we've been in touch with additional commercial vessels that are operating in the area as well as initiating the movement of additional Canadian Coast Guard assets and US Coast Guard surface assets into the area over the course of the next couple of days."

The US Coast Guard also has been in touch with the US Navy and the Canadian military to determine what underwater rescue capability is available, if needed, Mauger said.

OceanGate is assisting in the search and said it is "exploring and mobilizing all options to bring the crew back safely.

Concannon said officials were working to get a remotely operated vehicle that could reach a depth of 6000 metres to the site as soon as possible.

Action Aviation confirmed that its company chairman, UK billionaire businessman Hamish Harding, was one of the tourists on board.

READ MORE: 'System failed Josh at every level': Man with disability dies after being detained at train station

The company's managing director, Mark Butler, told the AP that the crew set out on Friday.

"Every attempt is being made for a rescue mission. There is still plenty of time to facilitate a rescue mission, there is equipment on board for survival in this event," Butler said.

"We're all hoping and praying he comes back safe and sound."

Harding is an adventurer who holds three Guinness World Records, including longest duration at full ocean depth by a crewed vessel.

In March 2021, he and ocean explorer Victor Vescovo dived to the lowest depth of the Mariana Trench.

In June 2022, he went into space on Blue Origin's New Shepard rocket.

The initial group of tourists was funding the expedition by spending anywhere from $US100,000 to $US150,000 ($146,000 to $219,000) apiece.

The latest trip was scheduled to depart from St John's, in the Canadian province of Newfoundland, in early May and finish up at the end of June, according to court documents filed by the company in April with a US District Court in Virginia that presides over Titanic matters.

READ MORE: Wedding couple mourning deaths of 10 guests thank community for 'love and support' 

Unlike submarines that leave and return to port under their own power, submersibles require a ship to launch and recover them.

OceanGate hired the Canadian vessel Polar Prince, a medium duty icebreaker that was formerly operated by the Canadian Coast Guard, to ferry dozens of people and the submersible craft to the North Atlantic wreck site.

The five-person submersible, named Titan, is capable of diving 4000 metres.

"With a comfortable safety margin," OceanGate said in its filing with the court.

It weighs 9072 kilograms in the air, but is ballasted to be neutrally buoyant once it reaches the seafloor, the company said.

READ MORE: Philanthropist Lady Primrose Potter rescued from Yarra after car veers off road 

The Titan is made of "titanium and filament wound carbon fibre" and has proven to "withstand the enormous pressures of the deep ocean," OceanGate stated.

OceanGate told the court that Titan's viewport is "the largest of any deep diving submersible" and that its technology provides an "unrivalled view" of the deep ocean.

Chris Parry, a retired navy rear admiral from the UK, told Sky News that the rescue taking place was "a very difficult operation".

"The actual nature of the seabed is very undulating. Titanic herself lies in a trench," he said.

"There's lots of debris around. So trying to differentiate with sonar in particular and trying to target the area you want to search in with another submersible is going to be very difficult indeed."

Timeline: How the expedition unfolded

Friday, June 16

• The Polar Prince departs St John's, Newfoundland, with the submersible Titan on board

Sunday, June 18

• The Polar Prince reaches the submersible launch site
• One hour and 45 minutes later communications with Titan are lost
• The vessel is reported overdue at 9.13pm local time (12.13pm Monday AEST)
• A rescue mission is launched involving the US Coast Guard and Canadian Coast Guard

Monday, June 19

• Rear Admiral John Mauger of the US Coast Guard says the submersible has between 70 and 96 hours of oxygen left
• It's confirmed the submersible had the full complement of five people on board, including UK billionaire Hamish Harding

READ MORE: Wedding couple mourning deaths of 10 guests thank community for 'love and support' 

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– Reported With CNN

Customers say they have been left in shock after being told that they'll be hit with a massive hike to their electricity rates next month – with some facing increases of up to 83 per cent.

AGL customer Judy Saunders, from Ashfield in Sydney's Inner West, said she was stunned when she received an email from the power company last week, informing her of the new electricity rates she would be charged from July 1.

"It was 51 per cent more than what I'm paying now – I just couldn't believe it," she told 9news.com.au.

READ MORE: Billionaire among five missing on vessel headed to Titanic wreck

Saunders said she had been on a single-rate plan for the past 12 months after her family had moved back into their newly renovated home.

From July, her electricity rates will surge from 16.5 cents per kilowatt hour to 24.98, with a credit of 5 cents per kilowatt hour for unused solar energy sent back to the grid.

Saunders acknowledged she had been on a seemingly cheap rate prior to the hike.  

"As the cost of living went up, I started shopping around, and every time I went to one of those comparison websites, the usual response was you are getting it better than anywhere else, stick with what you have got.

"So that's what I did, but now obviously all my good luck has run out."

Contact reporter Emily McPherson at Sign up here to receive our daily newsletters and breaking news alerts, sent straight to your inbox.

When Jemma Juckes was 19, she was diagnosed with Hodgkin's lymphoma, a form of blood cancer.

After treatment, she was given the all-clear but when she started getting shooting pains down her leg this year, she was worried the disease had returned.

She was sent for tests and was given even more crushing news.

READ MORE: Billionaire among five missing on vessel headed to Titanic wreck

READ MORE: A 'gift' in the mail after Paula's 50th birthday saved her life

The business owner was told she has terminal lung cancer which had spread around her body – and it's not a relapse of her earlier illness.

In fact, it could have been caused by her treatment for Hodgkin's lymphoma, doctors told her.

Juckes, now 32, said the fresh diagnosis just last month was "mind-blowing" – but she's staying positive.

"I don't even have words," she told 9news.com.au.

"I got told that it's terminal and they have given me a timeframe of 12 to 18 months, but I'm going beat this," she said.

READ MORE: Superfit mum-of-four Carly ran 10km a day before a strange symptom 'saw her world cave in'

Teen illness left her fearing the worst

Juckes, from North Kellyville, now owns a pizza shop in Glenorie, in Sydney's outer north.

She had been anxious about her health since facing Hodgkin's lymphoma at 19.

She had recovered from the highly treatable disease but was having blood tests twice a year to check it hadn't returned.

But despite that, as well as a full health check three years ago because she wanted to start trying for children with husband Lang, 36, nothing indicated any issues.

Juckes said she always thought something might be wrong with her because she often felt overly out of breath after running or took longer to get over colds.

But she always dismissed her worries.

"I didn't know if it was my anxiety playing games," she said.

However, when she woke up one morning a few months ago with shooting pains down her leg, she went to see her GP.

READ MORE: Teen smoking increasing for first time in decades

She was sent for more tests and told by her GP "not to worry" as she was likely suffering from the common back condition sciatica.

But her family doctor later told her she had three tumours on her spine and that her blood cancer could have returned.

More scans at Sydney Adventist Hospital, near Hornsby, found she actually has a new form of the disease – a rare small cell lung cancer, which has spread.

That's despite having almost none of the symptoms.

Do you have a story? Contact journalist Sarah Swain at ss****@******om.au

'Numb' reaction to shock results

Juckes said the news was "devastating" to hear, especially as experts told her it could have been caused by treatment for her first illness.

"They think it started from my previous treatment – they think maybe the radiation disrupted some cells," she said.

"The CT scan showed up that I have cancer on my lung, liver, lymph nodes and my spine and hip bone.

"I can't even begin to describe … you almost go numb."

Medical oncologist Dr Steven Kao from Chris O'Brien Lifehouse said it's hard to say whether Juckes' earlier cancer treatment had caused the new disease.

"All we can say is radiation is a risk factor and I guess when somebody so young gets this disease, you do wonder about that," Kao said.

Non-smokers can get lung cancer too

Most Aussies diagnosed with lung cancer have smoked but Juckes never has.

One-in-three women and one-in-10 men diagnosed with the disease never have, Lung Foundation Australia says.

Her diagnosis is even more poignant as her mother Lynn, 64, has just beaten breast cancer for the second time.

Juckes has started months of chemotherapy and immunotherapy every three weeks.

She's also seeing doctors at Chris O'Brien Lifehouse and says she'll do whatever she can to battle the disease.

"I just think I will beat this. I will go down whatever path I get told to go down," she said.

READ MORE: Parents diagnosed with cancer within hours of each other

Family 'shattered' to see sister suffer again

Juckes' sister, digital marketer Elise Pride, 34, said to see her sibling face the diagnosis again is "shattering".

"The first time around she was so young, just out of high school, that was probably one of the first times our family had been exposed to cancer," she said.

"We didn't think we would ever have to deal with it again.

"When she got told about the terminal diagnosis, that was soul-crushing."

Pride's husband, Gus, is tackling a charity walk to raise money towards Juckes' treatment.

READ MORE: Woman diagnosed with breast cancer at 25 shares urgent message

Lung cancer facts

Over the past few decades, the rates of lung cancer in women compared with men have been rising, according to studies.

That is being attributed to the fact most women took up smoking later than men when it was still a popular habit that peaked in the 1970 and '80s.

In Australia, lung cancer kills around 28,000 men and 22,000 women a year, making it the nation's biggest cancer killer.

It's the fourth most-diagnosed cancer in both men and women but remains rare in younger people.

Overall, more Aussies die of lung cancer than breast, prostate and ovarian cancers combined.

A new lung cancer screening test is in the works for those most at risk.

Early symptoms of lung cancer

• A cough which doesn't go away
• Shortness of breath
• Coughing up blood or phlegm
• Weight loss
• Hoarseness
• Fatigue

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Bebe Rexha has shared an update after she was rushed off stage at her concert in New York City when someone threw a mobile phone that hit her in the head on Sunday.

"I'm good," Rexha wrote in the caption of two photos she posted to her Instagram page that showed a closeup of the injury the singer suffered to her eye.

According to People magazine, a man in attendance was subsequently arrested and charged with felony assault for using his mobile phone as a weapon.

READ MORE: Search under way for missing submersible that takes people to see Titanic

CNN has reached out to the New York Police Department for comment.

Video of the incident shared by concertgoers on social media, Rexha grabbed her face and fell to her knees after she was hit while the crew at the Rooftop at Pier 17 rushed to help her.

Rexha has been on her "Best F'n Night of My Life" tour since May.

One concertgoer took to Twitter to write about the incident, saying, "This is Bebe Rexha being rushed out of the concert venue here in NYC after someone threw a f—ing phone and hit her face as she was leaving the stage. We were all having a hell of a good time and so was Bebe, we were all having a blast, I mean who would even do that??? We hope you're ok."

Another said, "Absolutely great show ruined by a fan throwing their phone at @BebeRexha hopefully she is ok after that."

Supporters came to the singer's defence, with one writing, "bebe deserves so much BETTER like come on. we love you girl."

Rexha has more concert stops in Philadelphia, Washington DC, Atlanta, Orlando and Houston.

CNN has reached out to representatives of Rexha for comment.

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Police have released new vision as they ramp up a search for the gunman who shot dead a 24-year-old in south-west Sydney. 

Barber and university student Marvin Oraiha was killed outside his home in Elizabeth Hills in May. 

Police believe the shooters used a white Audi as a getaway car, before dumping it in Green Valley. 

READ MORE: Search under way for missing submarine that takes people to see Titanic

They then got into a Toyota Prado before setting it on fire in Bonnyrigg Heights. 

Police are now looking for a third getaway car, believed to be a Honda Accord.

Criminal Groups Squad detectives released CCTV overnight showing two thin men dressed in dark clothing and balaclavas running down Cordelia Crescent in Green Valley before getting in the Prado and driving away.

The Prado was found burned out in Lewis Street in Bonnyrigg Heights while the Audi was found in Cave Close in Green Valley.

Anyone with information or dash cam vision was urged to come forward. 

CCTV released earlier in the investigation showed Oraiha's girlfriend, mother and sister walking inside after school pick-up before he was gunned down in the driver's seat of his car.

The shooting left him slumped over in the car and riddled with bullet wounds.

"I think it is as bad as it gets, it is an awful crime," detective acting superintendent Virginia Gorman said.

"It is shocking for the family, for the people who live in that street, for his girlfriend and generally the community."

Gorman said Oraiha's girlfriend was not in the car but had been with him shortly before the shooting.

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Philanthropist Lady Primrose Potter has been carried up the banks of the Yarra River by a heroic stranger after her Mercedes veered off a road and into the water in Melbourne.

The 92-year-old was driving her Mercedes E200 about 7pm on Sunday when she clipped another vehicle and ran off Alexandra Avenue and into the river.

She was able to open the door and make her way out of the knee-deep water with Paul Cavaiulo's assistance.

READ MORE: Australians will vote on Voice after referendum bill passes Senate

Cavaiulo witnessed the incident and said Potter had clipped his car and "ploughed" into the river.

"She just couldn't pull herself up the bank so I just kind of dragged her up," he said.

"She was a bit shaken up as well."

READ MORE: Dashcam footage captures out-of-control Tesla narrowly missing traffic

The arts philanthropist and high-society dame was taken to The Alfred hospital for observation and treatment suffering only minor injuries.

Police are continuing to investigate the crash.

Potter is expected to undergo a licence review, police said.

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Two people working at a restaurant have been allegedly grabbed around the neck by a 31-year-old man who stormed into their workplace.

Police allege the "intoxicated man" was involved in an altercation with staff at the Masala Bay restaurant on Victoria's Great Ocean Road about 9pm on June 10.

CCTV captured the moment the man allegedly stole a wallet and money from the register, leaving staff shaken.

READ MORE: Socialite rescued from Yarra after car veers off road

Police also alleged the man threatened security at a nearby hotel after being asked to leave and caused damage to the doors of the business before he was arrested.

The 31-year-old Diamond Creek man has been charged with multiple offences including affray, theft, unlawful assault, possess controlled weapon, criminal damage and make threat to kill.

He has been bailed to appear in Colac Magistrates' Court on October 9.

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Motorists are being advised to avoid the area, between Kaiapo Rd and Lowe St.

The surgeons believe the policy ‘shifts the dial’ and will bring about positive change