The U.S. Coast Guard announced via Twitter early Thursday that a remotely operated vehicle (ROV) deployed by the Canadian vessel Horizon Arctic has reached the sea floor, beginning its search for the missing submersible.

Meanwhile, the French vessel L'Atalante is preparing its ROV to enter the water in the search area, the U.S. Coast Guard said.

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

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."