A submersible named Titan went missing on Sunday in an expedition to see the wreckage of the Titanic. On Thursday, U.S. Coast Guard Rear Adm. John Mauger said the sub experienced a “catastrophic implosion,” according to CNN.

Stockton Rush, Shahzada Dawood, Suleman Dawood, Hamish Harding and Paul-Henri Nargeolet are presumed dead, per NBC News. The Coast Guard said the debris searchers found indicated the vessel’s implosion.

Everything to know about the sub Titan — and its voyage to the Titanic wreck

“I’m struck by the similarity of the Titanic disaster itself, where the captain was repeatedly warned about ice ahead of his ship and yet he steamed at full speed into an ice field on a moonless night and many people died as a result. For a very similar tragedy, where warnings went unheeded, to take place at the same exact site with all the diving that’s going on all around the world, I think is just astonishing,” James Cameron, director of “Titanic,” told ABC News.

Cameron’s “Titanic” won best picture in 1998. The director has taken 33 dives himself to the wreckage of the Titanic, according to CNN.

Behind Cameron’s motivation to make the film was his desire to dive down to the wreckage, which was discovered in 1985. “The Titanic was the Mount Everest of shipwrecks, and as a diver I wanted to do it right. When I learned some other guys had dived to the Titanic to make an IMAX movie, I said, ‘I’ll make a Hollywood movie to pay for an expedition and do the same thing.’ I loved that first taste, and I wanted more,” Cameron said, per CNN.

On one of his visits to the Titanic wreckage, Cameron told USA Today that he saw the Straus Suite. When he was making the film, he had to make educated guesses about what he didn’t know and said the real Straus Suite “looked just like the fake set that we got built.”

Missing Titanic submersible updates: Passengers and pilot presumed dead

James Cameron’s deep dives

Cameron himself has helped design a submersible known as the Deepsea Challenger — a 24-foot-long sub that had several cameras. He took the sub to the ocean floor of the Marianas Trench, per NPR.

The Marianas Trench is considered the deepest trench known on earth and it’s located east and south of the Mariana Islands in the Pacific Ocean. Britannica said, “An arcing depression, the Marianas Trench stretches for more than 1,580 miles with a mean width of 43 miles.”

“Surface, this is DEEPSEA CHALLENGER. I am on the bottom. Depth is 35,756 feet ... life support’s good, everything looks good.’ Only now does it occur to me that I might have prepared something more memorable, like ‘One small step for man,” Cameron later wrote when he reflected on his call to the ship after reaching the ocean floor, according to NPR.

When Cameron completed the dive, he broke the record for the deepest solo dive, NBC News reported. He also became the first person to reach the bottom of the Marianas Trench by himself.

Cameron has also said going into the deep sea can be dangerous — he said his vessel underwent testing and had backup gear for power. “You’re going into one of the most unforgiving places on earth. It’s not like you can call up AAA to come get you,” he told The New York Times.