Nitpicking, but Gore-tex is not an insulating material. And most coats waterproofed with Gore-tex are shells and you wear insulating layers beneath. For folks that spend time outdoors, typically those insulating layers beneath are wool or synthetic. You end up with two benefits: First, the Gore-tex can keep you dry for quite a while. If it does wet through, then you have insulation that works even while wet.
The tubes wouldn’t work well but other inflatable rafts could have been helpful. Just like a sufficient number of deployable life boats. Inflatable rafts may have helped by occupying less space, but that would require a reasonable method of inflating them, on top of the rafts being made to spec instead of built from inferior materials. Of course the entire ship being built to spec probably would have helped also.
Even very thick survival suits they carry on fishing boats don’t keep you alive in cold water past 15 minutes . The boats on deadliest catch carry those suits and they practice putting them on but they note it probably won’t save them.
A long time ago I heard some smart ass say the orange suits don’t keep you alive, they just make it easy to recover your body, so your wife can collect the insurance.
Correct. Yes, of course they had insulation other than just Gore-tex. Gore-tex was the outer layer for waterproofing.
What the holy hell is that thing? Some sort of steampunk war machine? 
Yep. Pretty much all cold-weather survival advice revolves around “Don’t be both wet and cold”. Traditional Inuit clothing is actually designed to help prevent sweating, and to avoid letting sweat soak into your clothes.
What if we put the inflatable tubes on a treadmill?
That would work, assuming you had something in the middle of the North Atlantic to mount the treadmills on.
How about mounting the treadmills on inflatable tubes?
Then the iceberg will definitely not take off.
If I recall correctly from my naval officer days, when we did a MOBEX (man overboard exercise), we had to maneouvre the ship and get the dummy out of the water within 7 minutes.
Seriously! How do you know the guy didn’t fall overboard totally by accident? There’s no reason to demean him like that when he so barely escaped death. What if you just slipped and fell somewhere, should everyone just laugh and say look at the dummy on the floor? A little mutual respect will go a long way you know.
I assume you’re joking but, if not, here’s the dummy:
I think the only way to save a significant number of extra passengers in the OP scenario would be to lower groups of people with already inflated inner-tubes in the available lifeboats to the water line, have them jump into the water on top of the tubes (without getting too wet), then raise the lifeboats and repeat the process until the final lifeboat drop carries off the final crew and passengers.
But, how to do this realistically? It would take keen foresight (starting the process almost immediately after impact), clockwork coordination, ability to quell panic and a lot of luck.
If each passenger was given a tube and had ~2 hours to inflate it and crew coordinated the lifeboat drops/elevations, more lives could have conceivably been saved as per the OP.
If the crew were truly evil, they could give tubes to the steerage passengers to inflate, under the premise they could use them to save their lives, then shoot them. Then they’d have more inflated tubes to give to the other passengers and themselves.
But it is fun to ponder.
My immediate reaction was to consider that too.
It is a classic back-of-the-fag-packet calculation I mean, 2 thousand inflated tubes stored in a hold, enough for all passengers! but what would be the benefit if they remained in that hold?
To what extent would they provide additional bouyancy and save the ship from sinking in the first place?
Unfortunately, not much I don’t think.
Assume each tube provided an additional half cubic metre of volume (that’s a big tube) and that they were in a hold that was infiltrated by the leak.
That means that enough inflated tubes to save everyone might displace a thousand tons of incoming sea water.
Unfortunately there were likely about 400 tons coming in per minute and about 38,000 tons in total was taken on before the ship sank.
So the sinking may be delayed by a couple of minutes.
I suppose one benefit might be that once under water, and for as long as the tubes remained intact, the plunge to the bottom may be slowed slightly.
Fair to say though that that is a modest benefit at best.
Or, we could ask how many inflated tubes would be needed to stop the sinking. I guess something approaching that 38,000 cubic metres would definitely do it, tens of thousands at least.
That would probably pose some storage challenges and may detract from the overall elegance of the cruise, I’m picturing this.
Which would have made sketching Kate Winslett’s boobs more of a challenge and somewhat less tasteful.
Only at first. Water pressure increases with depth, 1 atmosphere per 33 feet in seawater. So the tubes get compressed as the ship sinks farther and farther; after descending just 300 feet, that thousand tons of buoyancy at sea level is reduced to 100 tons of buoyancy. After 1000 feet, it’s just 3 tons of buoyancy, and there’s still another 11,000 feet to go before hitting bottom.
bugger, I knew something like that would happen but it is incredible to what degree water pressure gets very serious, very quickly.
I guess it just isn’t something that most humans experience to a meaningful degree.
Gaining a thousand feet in altitude might make you gasp a little more (and many of us do that regularly) but it takes very little depth to put you in huge difficulties (and very few of us ever do that)
I think a lot of it has to do with the fact that we are “above-water-living” creatures 
…
wales etc seem to have little problems getting deep … and (contraticting myself now) also apnea divers can go as deep as 100m / 300ft without falling apart …
the fact that we are 70something% made of water seems to be key here