Deep-sea vehicle industry insiders say the combination of the enormous depth, the lack of communication and the rapidly dwindling window of opportunity make rescue of the five people aboard the OceanGate highly unlikely.

The OceanGate was bringing its passengers to see the wreckage of the Titanic, about 12,500 below sea level, when it went missing on Sunday. 

The OceanGate has about 40 hours of oxygen remaining, the Coast Guard reported Tuesday afternoon, assuming the vehicle did not suffer an instant catastrophic explosion, as some experts have said they fear.

SUBMERSIBLE SCIENTIST FEARS OCEANGATE MAY HAVE SUFFERED CATASTROPHIC IMPLOSION: ‘DEEPLY WORRISOME'

"The math is not great," one career expert in autonomous underwater vehicles, more commonly known as drones, told Fox News Digital.

Only a handful of known manned vehicles exist in the world that are capable of diving to such depths and offering an opportunity for rescue. But none, according to reports, are close enough to offer assistance.

An unmanned operation offers the best hope — but a limited hope, the experts say.

"A drone could find the vehicle, but they would not be able to recover people. But there should be a way to attach a line. And they could potentially recover the vehicle that way," said submersibles engineer Steve Somlyody, who is based in Florida.

The lack of communication or sound since Sunday is deeply concerning, he said.

ONE OF PAKISTAN'S RICHEST MEN, SON, ABOARD MISSING OCEANGATE TITANIC TOURIST SUBMARINE

"If they are conscious, they would be tapping on the hull. But water is stratified. Sound does not move in a straight line. Sound can be distorted and blocked the same way water distorts light. So they may be very hard to hear."

He surmised that the U.S. Navy has repositioned a submarine to dive deep and listen for sound from the OceanGate. 

The Pentagon confirmed on Tuesday that it is assisting search operations, but cited only air assets, including three C-130s to fly over the areas.

OCEANGATE, COMPANY BEHIND MISSING TITANIC TOURIST SUB, ONCE SUBJECT OF LAWSUIT OVER SAFETY COMPLAINTS

"In addition to that, the Navy has been in touch with the Coast Guard and is working to provide personnel, such as subject matter experts and assets as quickly as possible," said Department of Defense Deputy Press Secretary Sabrina Singh. 

The OceanGate is far too deep for any traditional submarine to travel.

So a Navy submarine, if one was used, could only listen for sounds from the vehicle. 

Drones offer the only realistic opportunity to reach the OceanGate and possibly rescue its passengers, experts indicated.

"These are miraculous, extremely high-tech things," said the expert in autonomous underwater systems. 

"But for them to work with any other vehicle takes a lot of integration time and software work. To think you can just throw one of these in the ocean on a rescue mission — to me that seems not realistic."

He maintained that diving to Titanic depths for the purposes of thrills is inherently dangerous.

"It’s one of these super-rich adventure-guys kind of things. Anybody should do what they want. But I wouldn’t do it," he said. 

CLICK HERE TO SIGN UP FOR OUR LIFESTYLE NEWSLETTER

"These are not systems that have been formally approved by any kind of agency. I’m sure they had to sign their lives away."

Earlier this month, Argentine soccer superstar Lionel Messi stunned the soccer world when he announced his intentions to move to Major League Soccer and join Inter Miami CF following his exit from Paris Saint-Germain.

On Monday, Inter Miami CF owner Jorge Mas told reporters that the team's target date for Messi to make his highly-anticipated debut is set for July 21. Inter Miami is scheduled to play Cruz Azul on that date in a Leagues Cup match.

Messi is currently vacationing in Rosario, but Mas said preparations for Messi's arrival are already well underway. Mas noted that Inter Miami is working on increasing the stadium's seating capacity by around 3,000 seats.

CLICK HERE FOR MORE SPORTS COVERAGE ON FOXNEWS.COM

Inter Miami currently plays at DRV PNK Stadium in Fort Lauderdale, Florida.

"We have already contracted to fill in the corners of the stadium that should increase capacity by approximately 3,000 to 3,200 seats," Mas said. "We are gearing up to do that work in the next four weeks. Every game will be sold out. The demand for tickets has been 10 times what we can handle on a season ticket basis."

GUNMEN THREATEN LIONEL MESSI AFTER OPENING FIRE ON FAMILY SUPERMARKET: ‘WE’RE WAITING FOR YOU’

In the wide-ranging interview, Mas also mentioned that the MLS has not altered any rules in an effort to accommodate Messi's arrival.

"There are no categories or anything that is being changed to incorporate Lionel Messi on to Inter Miami’s roster," Mas said. 

Messi’s contract will be worth $50 million to $60 million per year, the team said Tuesday. But, he cannot sign until sometime in July, after his contract with Paris Saint-Germain expires.

Mas also said he hopes to start construction during the next two weeks on Miami Freedom Park, the team’s long-term home near Miami International Airport, and is targeting to have the venue open in the summer or fall of 2025, the Herald reported.

Inter Miami also plans to enhance security, bussing players into the stadium for games, Mas said.

Inter Miami has gotten off to a slow start this season, and currently has a 5–12 record with 17 points. The club is in last place in the MLS’s Eastern Conference and trails CF Montreal by seven points for the conference's ninth and final playoff spot.

The Associated Press contributed to this report.