I CAN only hope against hope that those aboard the missing Titanic sub can be rescued — but while I can only imagine their terror, I certainly know the dangers.
They were explained to me when I made the perilous journey myself for The Sun.
We were told just the tiniest of things going awry could see us cut in two by a powerful jet of water or crushed under the weight of the Atlantic Ocean.
The cramped capsule could even be engulfed in fire.
Oh, and there was a slim chance of rescue if it all went wrong.
I vividly recall how trepidation and claustrophobia battled with a rising sense of excitement as the hatch was slammed shut and we bobbed nauseatingly on the surface waiting to descend to the inky depths below.
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My dive to the wreck, two miles beneath the surface, came in July 2001 when fascination with Titanic was still at fever pitch after James Cameron’s 1997 blockbuster.
The risks had been drummed into us for days as the Russian research vessel RV Akademik Keldysh took us from St John’s, in Newfoundland, Canada, to where the liner sank on April 15 1912.
Dives were being conducted by Moscow’s Shirshov Institute of Oceanology — using the two three-man submersibles Mir 1 and Mir 2 featured at the start of the movie.
The small bathyspheres were two of only five vessels in the world at the time capable of diving to the bottom of the Atlantic.
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So it clear in an emergency there were no handy vessels coming to our rescue.
A British businessman bought the rights to one expedition to promote his new diving website, and offered dives as prizes for various media outlets.
I was accompanying Peter Bailey, the grateful winner of The Sun’s competition.
Skipper of the Keldysh, Dr Anatoly Sagalevich, had appeared in the Titanic movie.
He outlined how the oxygen-enriched atmosphere in the pressurised subs raised the risk of a blaze.
So we would be kitted out in fire-retardant to protect us — for a few extra seconds.
Then there was the extreme pressure we would face.
Equivalent to around 380 atmospheres or 5,584psi, it meant if the Mir developed a pin-prick fracture the laser-like jet of water forced through the hole would able to slice a man in half.
But, with black humour, he said we should not worry because it would only be milliseconds before the Mir imploded completely.
At the end of the first day, as the sea turned choppy, Peter and I watched Russian divers struggle to recover the two Mirs from the water at the end of their eight-hour dive.
A wooden launch vessel was picked up by a wave and slammed down on top of the one in which we were due to visit Titanic.
When it was eventually winched aboard, I could see the tail fin, aerial and propeller housing had been smashed.
I feared future dives would be cancelled but, after a night in the ship’s workshops, the submersible was ready for launch again.
To my alarm it had been patched up with silver duct tape.
When it came to our turn we climbed a ladder and then, with only room to lie on bunks either side of the Russian pilot’s seat, we readied ourselves as a crane lowered us into the water.
We began to descend. Within a very few metres, any light from the surface had gone.
The pilot switched on headlights for us to see the sea life through our 7in thick plexiglass portholes.
After a short while they were turned them off to conserve precious battery power.
For the next two hours we sat in darkness as we descended, talking to the pilot and listening to the regular ping of the sonar.
Once on the sea bed our pilot put the lights on to illuminate a colourless lunar-like sandscape.
But within minutes we were confronted by a wall of black.
Then we rose and rose until suddenly, just an arms-length away, on the other side of the porthole glass, was the unmistakeable bow rail of Titanic.
Our pilot skilfully navigated us around Titanic’s remains, close enough to see her but respectfully distant enough not to disturb her.
After we had marvelled at the forward section we passed over the debris field to the stern section and past the giant engines.
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Only when the pilot announced we had to return to the surface did we realise we had been down there for four hours.
As we began the two-hour return to the surface, the Mir’s lights were turned off and Titanic went back to darkness once more.