An extensive search and rescue operation continues Tuesday to locate a submersible that went missing during a mission to view the Titanic shipwreck, but many have become concerned with the seemingly improvised construction of the vessel. The expedition off the coast of Newfoundland, hosted by U.S. company OceanGate Expeditions, was reported overdue shortly after 9 p.m. local time Sunday evening and above-water crews have not been able to contact the vessel.
The carbon-fiber and titanium vessel called the Titan has diving capabilities of more than 13,000 feet and can carry five people to the Titanic wreck in the Atlantic Ocean. It had run successful trips to the site in 2021 and 2022, according to the company’s website.
However, video shared to social media Monday by a CBS reporter has raised concerns about how sound the Titan’s construction really is.
In 2022, David Pogue took a closer look at the Titan, and said he “couldn’t help noticing how many pieces of this sub seemed improvised, with off-the-shelf components.”
You may remember that the @OceanGateExped sub to the #Titanic got lost for a few hours LAST summer, too, when I was aboard…Here’s the relevant part of that story. https://t.co/7FhcMs0oeH 
A news report from that time shows Pogue signing a waiver that says the submersible is “experimental” and “had not been approved by any regulatory body.”
The segment, which aired on CBS Sunday Morning, shows Pogue climbing into the Titan, which he described as being “about the size of a minivan.” Inside was a single green button that OceanGate CEO Stockton Rush told Pogue “should be like an elevator. It shouldn’t take a lot of skill.” 
Also in the video, Rush points out what looks to be a handle inside the Titan, which he says he purchased from RV supplier Camping World. In perhaps one of the more shocking revelations, he says “We run the whole thing” using a Logitech video game controller.
Rush also says the system that maintains air pressure underwater is “not MacGyvered at all” and was developed with the help of NASA and Boeing.
That said, Pogue witnessed a failing of the Titan from the vessel’s above-water control room.
To be clear, I was not on the sub that day—I was on the ship at the surface, in the control room. They could still send short texts to the sub, but did not know where it was. It was quiet and very tense, and they shut off the ship’s internet to prevent us from tweeting.
“There’s no GPS underwater, so the surface ship is supposed to guide the sub to the shipwreck by sending text messages,” Pogue said in the clip.
“But on this dive, communications somehow broke down. The sub never found the wreck.”
A Smithsonian Magazine article from 2019, which calls Rush a “daredevil inventor,” has also raised concerns.
In the piece, Rush discusses the lack of underwater exploration in the world’s oceans, explaining the 1993 Passenger Vessel Safety Act — which imposed strict manufacturing and inspection requirements on tourist subs and prohibited dives below 150 feet — “needlessly prioritized passenger safety over commercial innovation.”
“There hasn’t been an injury in the commercial sub industry in over 35 years. It’s obscenely safe, because they have all these regulations. But it also hasn’t innovated or grown—because they have all these regulations,” Rush told the magazine at the time.
In a blog post from 2019, OceanGate said the Titan wasn’t classed by an independent group that sets safety standards because its technology was so new and that their innovation “falls outside of the existing industry paradigm.”
It said by not having the vessel classed they were avoiding a “multi-year approval cycle due to a lack of pre-existing standards.”
Classing usually checks if vessels meet standards in buoyancy, number of life rafts and hull materials, the blog post said. The post said that while classing has a safety value, it is “not sufficient to ensure safety.”
Five people are reported to be onboard Titan, and the submersible had a 96-hour oxygen supply when it was put to sea at roughly 6 a.m. Sunday, according to David Concannon, an adviser to OceanGate.
Theoretically, that supply should last until Thursday afternoon, eastern time.
Canadian research icebreaker Polar Prince, which was supporting the Titan, reportedly lost contact with the vessel roughly an hour and 45 minutes after it submerged.
What caused it to lose contact with the Polar Prince is not clear.
The U.S. Coast Guard said one pilot and four “mission specialists” were aboard. Those mission specialists are people who pay a reported US$250,000 apiece to go along on OceanGate’s expeditions. They take turns operating sonar equipment and performing other tasks in the five-person submersible.
The Polar Prince was scheduled to do surface searches throughout Monday and a Canadian P3 Aurora aircraft was resuming its sonar searches in the morning, the U.S. Coast Guard said on Twitter. Two U.S. Lockheed C-130 Hercules aircraft also have conducted overflights.
The Canadian military also dropped sonar buoys to listen for any possible sounds from the Titan.
Pengfei Liu, a professor of Marine Hydrodynamics at Britain’s Newcastle University, told NBC News that the apparent lack of signal from the vessel is “very worrying.”
He said that the submersible should be sending out a signal every few minutes, but it’s not known if OceanGate has detected any recent signals.
“No signal is very bad news,” said Liu, explaining that if the Titan’s hull collapsed under the enormous pressure “then survival chances are zero.”
Alistair Greig, a professor of marine engineering at University College London, echoed Liu’s thoughts, saying a leak in the pressure hull would certainly result in a poor outcome.
“If it has gone down to the seabed and can’t get back up under its own power, options are very limited,” Greig said.
However, he also mentioned a simpler scenario: “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.”
OceanGate’s website describes the Titan as a combination of “ground-breaking engineering and off-the-shelf technology,” the latter of which “helped to streamline the construction, and makes it simple to operate and replace parts in the field.”
In a May 2021 court filing, OceanGate said Titan had an “unparalleled safety feature” that assesses the integrity of the hull throughout every dive.
— With files from Global News’ Aaron D’Andrea and The Associated Press