A search is underway for a missing sub that carries people to view the wreckage of the Titanic.

Canadian officials say the five-person submersible was reported overdue Sunday night about 700 kilometers south of St. John’s, Newfoundland and that the search is being led by the U.S. Coast Guard.

“The equipment gets better, the technology gets better, so I’m very hopeful, I’m very positive I mean I was in a sub for 12 hours we have our own breathing system on board, and if that’s maintained properly, like changing your filter on your Co2, you can stay down there for quite a few hours,” said Larry Daley, a Titanic explorer based in Newfoundland.

The missing submersible can travel to a depth of 4,000 meters and has enough oxygen for 96 hours for the crew.