Titanic sub search: Fate of missing Titan submersible's passengers may rest on one man

If the submersible now missing in the icy seas of the North Atlantic is still intact, the fate of the five men inside may rest on one crew member - a highly experienced mariner from France called Paul-Henri Nargeolet.

Nargeolet knows the sea - the 77-year-old spent two decades in the French Navy, serving as a deep-sea diver, an underwater mine clearer and a submarine pilot.

He also knows the Titanic - perhaps better than anyone else on Earth.

He has participated in some 35 dives to the resting place of the doomed passenger liner and runs a company which owns the salvage rights and displays artefacts at special exhibitions.

This famous mariner has many friends and admirers, among them a seafarer called Jose Paulo Viera da Silva.

This Portuguese captain, who has piloted oil tankers and merchant ships for over 30 years, is well acquainted with Nargeolet - and he respects his knowledge and his nerve.

"You can see that he is very experienced. When he [conducts] missions at sea he doesn't have problems and I believe that he will be one of the solutions to this situation."

According to the Portuguese, Nargeolet will draw on lessons learned from a life both at and under the sea.

"Do you think he could find a solution to this?" I asked.

"I think he will help, of course. I think he can [work with] the other people on board so they can have a good expectation to come to the surface."

"You believe that, even now, with oxygen supplies running out on [the submersible] Titan?" I asked.

"Yes, I will believe this to the last moment. And I hope and I wish this (as well) because it would be pity if we lose that man - and the others - I know this man very well."

Da Silva captained the supply boat which took Nargeolet and an American film crew to the site of the Titantic in 2010.

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When they reached the site, they put an autonomous submersible loaded with specialist equipment into the water. However, the vessel got snagged on the wreck. Da Silva still remembers how Nargeolet kept his cool.

"The team were very experienced but the (submersible) got stuck on a piece of the Titanic. We had to do a lot of manoeuvres to be able to bring it back. It got stuck in the wreck - it was the worst part and everyone was afraid we'd lose it."

It would take a special person to survive in the cramped conditions of a craft like Titan but Captain da Silva says, if anyone can get through this, it is Paul-Henri Nargeolet.

"He's a very quiet person so I think he can keep the others calm because it is important to save oxygen and not (make) any effort.

"It is not easy of course but he is a quiet person and I think he will be a leader of the people who are there."