The water inside your proposed flooded submersible would be at the same pressue as the water outside, so the people would be crushed just as if they were outside the sub I fear.
That's putting it clearly and very well across, thank you.
Mr Bojangles, to further explain what Mr Goodwin has already said above, the actual water pressure where the wreck of
Titanic now lies is about 6000 PSI or around 400 times the atmospheric pressure. But
that is the same inside and outside the wreck with water freely 'flowing' in and out - although it may not actually be flowing as such. That means, despite the enormous
actual pressure, the
pressure difference will be zero; it is such a
gradient which is likely to cause an implosion or explosion, which clearly does not exist here.
When the
Titanic broke apart at the ocean
surface, the actual pressures were about 15 PSI, which is hardly felt by the human body or anything else. The bow was already flooded and like the stern section, its own deck spaces were also exposed after the break-up. So, as the bow sank, the actual water pressure rapidly increased as it always does,
but it did so equally both inside and outside, which were therefore
pressure equilibrated right till the bow reached the bottom of the ocean, and so it remains today. Therefore, no implosion or explosion.
A
nearly similar would have been effect with the stern section, despite the fact that it was mostly dry till the break-up. The deck spaces were exposed here too and so very rapid flooding would have started while the stern section was still at the surface, where it remained for between 1 and 2 minutes IMO before disappearing beneath the surface. During that time most, if not all the air within the stern section would have been forcibly displaced by the flooding water and that process would have continued as it sank. By the time the external water pressure became high enough to potentially exert implosive forces on the stern section, almost all the air would have been displaced by water and so the pressure
difference between the spaces inside and the sea outside would have been very low. So again, no implosion.
It is theoretically possible that small air pockets remained deep within the stern section as it approached the ocean floor, but as air is compressible and compression increases pressure, the pressure of those air pockets could have increased exponentially.
IF that had happened - and it is no means certain that it did - that pressurized air could have been suddenly forced out when the stern struck the bottom. In that case, the forces would have been
explosive, ie from inside to outside - probably contributing to the mangled state of the stern section.
But with the
Titan, the hull breach occurred probably at around 9000 feet at a stage when the external pressure was enormous and enough to kill a human being within a fraction of a second. Up until then, the pressure within the sub would have been low enough for human comfort, but separated from the enormous pressure building up outside by the
Titan's pressure hull. When that failed, the 5 occupants would have been exposed suddenly to water under huge pressure leading to instantaneous death.
I hope that this clarifies things.
