A former passenger who visited the Titanic wreck site on board OceanGate’s now-missing Titan submersible craft says everyone involved in the deep sea journey was "intimately informed" how much of a "dangerous mission" it was. 

Fred Hagen spoke to "Fox & Friends" Wednesday morning as the Coast Guard estimates there is less than 24 hours of oxygen remaining in the Titan, which vanished Sunday on an expedition to visit what remains of the Titanic. 

"There were safety protocols in place. I know there is a big controversy now that there has been a catastrophe, people are second-guessing and wondering why there weren’t backup systems," said Haden, a businessman and explorer from Pennsylvania. "We were all told – intimately informed – that this was a dangerous mission that could result in death and injury. So that was well understood.

"We were versed in how the sub operated, we were versed in various protocols – but it’s not a safe operation inherently," he added. "And that is part of research and development and exploration and experimentation." 

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Hagen also said, "If the Wright brothers had crashed on their first flight, they would have still left the bonds of earth and they would have crashed. They had no backup system and Stockton Rush is a visionary who is trying to democratize the depths, trying to open up the ocean, and that was not possible without risk." 

Rush, the CEO of OceanGate, is one of the five people currently missing aboard the vessel.

Hagen visited the wreckage of Titanic alongside French mariner Paul-Henry Nargeolet, another person who is missing. 

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He described Nargeolet as "one of the most wonderful, warm human beings I have ever met."

"He is a living legend in the deep dive community," Hagen said. "And even people I have heard that are critical of what OceanGate attempted to do agree that PH is one of the finest and most consummate professionals in the deep dive industry." 

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"I say that in the dearest hope that our good friend PH is alive today," Hagen added. 

It remains unclear what happened to the OceanGate Titan. 

"As long as there is the chance of them surviving and coming back to us alive we have to focus only on rescue.… We have to believe that we have to make every effort," Hagen told "Fox & Friends." 

"No one knows exactly what went wrong," he added. "If there had been a leak and an implosion they would have been killed instantly."