Five people were on board the Titan submersible when it lost contact with its support ship during a dive to the Titanic wreckage site in the North Atlantic on Sunday. On Thursday, the U.S. Coast Guard and the company that operated the submersible, OceanGate Expeditions, said that all five people on board were believed to be dead.

Here are the passengers who were aboard the craft.

Stockton Rush

Stockton Rush was the founder and chief executive of OceanGate Expeditions, the company that operated the submersible. He was piloting the vehicle.

Mr. Rush was a descendant of two signers of the Declaration of Independence, Benjamin Rush and Richard Stockton. He graduated from Princeton with a degree in aerospace engineering in 1984, according to his company biography.

In 2009, he founded OceanGate, a private company that is based in Everett, Wash., near Seattle.

In an interview that aired on CBS in November of last year, Mr. Rush said he grew up wanting to be an astronaut and, after he earned his degree, a fighter pilot.

“I had this epiphany that I didn’t want — it wasn’t about going to space,” Mr. Rush said. “It was about exploring. It was about finding new life-forms. I wanted to be sort of the Captain Kirk. I didn’t want to be the passenger in the back. And I realized that the ocean is the universe.”

Hamish Harding

Hamish Harding, a British businessman and explorer, holds several Guinness World Records, including one for the longest time spent traversing the deepest part of the ocean on a single dive. He wrote on his Facebook page on Saturday that he was proud to announce that he had joined OceanGate’s mission “on the sub going down to the Titanic.”

Mr. Harding, 58, was the chairman of Action Aviation, a sales and air operations company based in Dubai. He had previously flown to space on a mission by Jeff Bezos’s Blue Origin rocket company.

Mr. Harding also took part in an effort to reintroduce cheetahs to India, and holds a world record for the fastest circumnavigation of Earth via both the geographic poles by plane.

Paul-Henri Nargeolet

Paul-Henri Nargeolet, a French maritime expert, had been on more than 35 dives to the Titanic wreck site.

Mr. Nargeolet was the director of underwater research for RMS Titanic, Inc., an American company that owns the salvage rights to the famous wreck and displays many of the artifacts in Titanic exhibitions. The company conducted eight research and recovery expeditions between 1987 and 2010, according to its website.

Shahzada Dawood and Suleman Dawood

The British-Pakistani businessman Shahzada Dawood, 48, and his son, Suleman, 19, were members of one of Pakistan’s wealthiest families.

Mr. Dawood had a background in textiles and fertilizer manufacturing. His son was a business student at the University of Strathclyde in Glasgow, a spokesman for the school confirmed on Thursday.

Mr. Dawood and his son had “embarked on a journey to visit the remnants of the Titanic” when contact with the vessel was lost, the statement said, asking for privacy for the family.

Mr. Dawood was also on the board of trustees for the Search for Extraterrestrial Intelligence Institute. The organization said on its website that he was a resident of Britain, and a father of two children.