Time is running out as rescuers race to locate and save five people trapped in a submersible that vanished during a tour of the Titanic wreckage on Sunday morning.

The deep-sea vessel submerged at 8 a.m. ET on Sunday with a 96-hour oxygen supply, according to the U.S. Coast Guard. That amount of breathable air is forecast to run out on Thursday morning.

The search and rescue mission remains ongoing.

The New York Times traced the lineage of Wendy Rush, wife of missing OceanGate CEO Stockton Rush, and found that she's the great-great-granddaughter of a couple who died on the Titanic, Isidor and Ida Straus.

The executive director of the Straus Historical Society told ABC News that The Times article, which cites archival records, is largely correct with regard to Wendy Weil Rush's heritage.

-ABC News' Nic Uff

A U.S. Navy portable crane system capable of bringing up items from as deep as 20,000 feet has arrived in St. John's, Newfoundland, but is waiting to be welded onto a chartered ship to take it to the search area for the missing submersible, according to a U.S. Navy official.

The Navy has not yet contracted a ship for the salvage system, known as Fly Away Deep Ocean Salvage System or FADOSS, the official told reporters Wednesday. Once the ship is contracted, Navy teams will spend approximately 24 hours working around the clock to weld the system aboard the ship before it can leave port, the official said.

FADOSS is the salvage system the U.S. Navy uses for all of its deep-water recoveries. Last year, it was able to bring up an F/A-18 aircraft that had fallen into the waters of the Mediterranean Sea.

-ABC News' Luis Martinez

The co-founder and Board chair of Horizon Maritime, the company that owns the Polar Prince boat that took the Titan submersible out to sea, is speaking out.

"We have been supporting the Titanic expeditions for several years," Sean Leet said, calling the Polar Prince "an iconic former Canadian Coast Guard icebreaker that has been upgraded with advanced technology."

"All protocols were followed" for the submersible's mission, he said at a news conference Wednesday, calling the missing sub an "unprecedented" situation.

Equipment heading to search site can reach the depths of the submersible and potentially take it to the surface, he said.

"We wish to thank everyone involved in this rescue mission, especially the U.S. and Canadian Coast Guards, the organizations that have made their marina assets available including the French government … [and] the many private companies that have dropped everything at a moment's notice," Leet said.

"Our thoughts and focus remain with the crew of the Titan and their families," he said.

Leet said he is holding out hope that the five-person crew will be brought home safely.

"We'll continue to hold out hope until the very end," he said.

Digital marketing tycoon Chris Brown originally planned to go on Sunday's submersible tour of the Titanic wreckage but withdrew due to safety concerns. His friend, Hamish Harding, is among those aboard the missing vessel.

Brown, who described himself as a "modern day adventurer," admitted that he knew "very little" about the tour operator, OceanGate Expeditions, prior to signing up. But he said the deep-sea trip initially sounded "like a great idea."

"The Titanic's obviously an iconic wreck," Brown told ABC News' Michael Strahan during an interview Wednesday on "Good Morning America."

"OceanGate had put forward this program to go down and do a 3D scan of the wreck," he added. "So it's a chance for an expedition, exploration and adding a bit of science into the situation."

Brown said safety concerns ultimately led him to pull out of the trip, but he declined to go into detail.

"I'm not really sure that this is the time to be going into that sort of thing," he added. "I think that the focus right now has to be on trying to rescue these people. It's not fair on the families and friends to be making speculation about what might've happened or how it happened at this point."

Brown said he feels "no" apprehension about joining similar projects in the future but noted that it's important to "think about all the risks."

"If you don’t have an appetite for those risks, then you might not go ahead," he said. "You may try and mitigate those by bringing in some expertise from outside. You might have other risks or dangers that could be mitigated by changing the time of when you go out there."