The U.S. Coast Guard announced via Twitter late Thursday morning that "a debris field was discovered within the search area by" a remotely operated vehicle (ROV) "near the Titanic" wreckage.

"Experts within the unified command are evaluating the information," the U.S. Coast Guard tweeted.

The Coast Guard is set to hold a briefing on the findings from the Horizon Arctic's ROV at 3 p.m. ET.

Despite their onboard oxygen tank expected to be depleted sometime Thursday morning, one doctor says they may have more time if the passengers are still alive. He estimates the five people aboard the lost Titanic tourist sub could survive for 10 to 20 hours with air still circulating through the experimental capsule.

Dr. Richard Moon, a professor of anesthesiology at Duke University, said that despite conditions being dire, those aboard the OceanGate Expedition's submersible could extend the oxygen available after its tank is depleted by staying calm and moving as little as possible.

"The actual amount of time that they have is unpredictable, but it's probably less than 24 hours after the final oxygen in the tank is depleted," Moon, director of the Duke Center for Hyperbaric Medicine and Environmental Physiology, told ABC News.

Read more here.

-ABC News' Bill Hutchinson

The U.S. Coast Guard announced via Twitter on Thursday morning that a remotely operated vehicle (ROV) deployed by the French vessel L'Atalante has entered the water in the search area.

The U.S. Coast Guard also gave an update on the conditions at sea, saying winds were at 14 mph with gusts up to 19 mph, swells were 4 to 5 feet and the air temperature was 50 degrees Fahrenheit.

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.

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."