The family of the British-Pakistani father and son who were on board the ill-fated Titan submersible expressed their "profound grief" at their loss on Friday.
Shahzada Dawood, aged 48, and his son Suleman, 19, were among the five people on board the sub when it disappeared in the North Atlantic four days previously.
"It is with profound grief that we announce the passing of Shahzada and Suleman Dawood," said a statement from the Dawood Foundation, his family's charitable organization.
"We extend our heartfelt condolences to the families of the other passengers on the Titan submersible," the statement read, which was signed by Shahzada's parents, Hussain and Kulsum Dawood.
Hussain Dawood is among Pakistan's wealthiest men and heads up the Engro Corporation.
The Dawood Foundation thanked all parties who were involved in the rescue operations and said, "their untiring efforts were a source of strength for us during this time."
Also on board the vessel were British explorer Hamish Harding, French submarine expert Paul-Henri Nargeolet and Stockton Rush — CEO of the sub's operator OceanGate Expeditions.
Doomed trip to Titanic's resting place
The 21-foot (6.5-meter) Titan was due to resurface seven hours after beginning its descent at 8:00 a.m. on Sunday, but the craft lost communication less than two hours in.
A multinational search-and-rescue operation involving various vessels and aircraft from the US and Canadian coast guards, including a robot sent from France, joined the rescue operation.
The rescue effort included searching 10,000 square miles (around 20,000 square kilometers) of surface water.
On Thursday, the US Coast Guard said the vessel had suffered a "catastrophic implosion," killing all of those on board — likely in an instant.
The statement from US authorities followed confirmation from Rear Admiral John Mauger that debris found on the seabed, 1,600 feet (500 meters) from the bow of the Titanic, was consistent with there having been an implosion of the sub's pressure chamber.
The search for the missing submersible has become an investigation and salvage mission which officials say could take an indefinite amount of time to conclude.
The RMS Titanic sank in 1912 after hitting an iceberg during its maiden voyage from England to New York.
There were 2,224 passengers and crew on board and more than 1,500 people perished.
OceanGate Expeditions — the company which operated tours to the site of the doomed passenger liner — charged $250,000 for a seat on the sub.
"These men were true explorers who shared a distinct spirit of adventure, and a deep passion for exploring and protecting the world's oceans," the company said in a statement. "We grieve the loss of life and joy they brought to everyone they knew," OceanGate said.