Officials with Canada's Transportation Safety Board said at a press conference Saturday that they have begun speaking with people on board the Polar Prince, which launched the ill-fated Titan submersible.

The Polar Prince returned to its port, St. John's, Newfoundland, on Saturday morning.

"I would say that we've received full cooperation," TSB Director of Marine Investigations Clifford Harvey said. "It's been a really good interaction thus far and is really getting full cooperation with all the individuals involved."

In addition, the Royal Canadian Mounted Police (RCMP) said they are "examining the circumstances" of the deaths on board Titan, and will launch a full investigation if "the circumstances indicate criminal, federal or provincial laws may possibly have been broken."

-ABC News' Matt J. Foster

A defense budget expert estimates once the U.S. military participation concludes, the cost for the search and rescue mission of the five passengers on board the Titan submersible will cost the U.S. around $1.5 million.

Mark Cancian, a senior advisor with the Center for Strategic and International Studies, came up with the estimate based on aircraft sorties, cross referencing the U.S. Department of Defense cost numbers, Coast Guard Cutter costs and flying hour costs. He said some costs have already been set aside in various budgets, with resources simply diverted to the site.

He emphasized that these are strictly well-informed guesses.

A spokesperson for the Coast Guard's District 1 in Boston would not give an estimate of costs so far, saying, "We cannot attribute a monetary value to Search and Rescue cases, as the Coast Guard does not associate cost with saving a life."

-ABC News' Jaclyn C. Lee

The U.S. Coast Guard will be the organization leading the investigation into the OceanGate sub incident.

The NTSB announced the news on Friday via Twitter, noting it will "contribute to their efforts."

A Las Vegas father and son told ABC News OceanGate CEO Stockton Rush pressured them for months into taking two seats on the now failed mission to the Titanic, making bold claims about the vessel's safety.

Financier Jay Bloom shared text messages between himself and Rush where Rush dismissed concerns from Bloom and his son Sean about taking the trip on the Titan submersible.

"While there's obviously a risk it's way safer than flying in a helicopter or even scuba diving," Rush texted.

"He sort of had this predisposition that it was safe," Bloom told ABC News. "And anybody who disagreed with him, he felt it was just a differing opinion."

Bloom added that Rush flew out to Las Vegas in a homebuilt plane to convince him to attend the voyage aboard the submersible.

"He flew it all the way to Vegas. And I was like, 'This guy is definitely down to take risk,'" Bloom said.

-ABC News' Sam Sweeney

Rescuers racing against the clock to save the five people trapped in a tourist submersible nearly two miles deep in the Atlantic Ocean are facing major obstacles that could make saving the people onboard extremely difficult, according to a former U.S. Navy submarine commander.

Retired Capt. David Marquet told ABC News on Monday that this type of rescue operation is complicated because there aren’t nearby U.S. or Canadian underwater vessels that can go as deep as the Titanic wreckage, which sits 13,400 feet below the ocean’s surface. Also, the ocean is pitch black at that depth.

"The odds are against them," Marquet said. "There's a ship in Boston that has this ability to either lower cable and connect to it or have a claw. It's still a thousand miles away."

Even if a vessel was able to locate the submersible and lower a cable, it’s extremely difficult to safely navigate the waters and attach it, according to Marquet.

"You've got to get it exactly right," he told ABC News. "It's sort of like ... getting one of those toys out of those arcade machines. In general, you miss."

Rescuers do have one advantage, Marquet said, as weather conditions off the coast of Newfoundland are not rough and will not disturb any boat or vessel there.

Marquet added that if the five people aboard are still alive, they would be asked to sleep to conserve their oxygen.

"We would put the vast majority of the crew to sleep because that's when you're using the least amount of oxygen and you're expelling the least amount of carbon dioxide," he said.

-ABC News' Sam Sweeney and Ivan Pereira