I believe I read that the descent took 2 hours and they were 1 hour and 45 minutes into it when they lost contact, so were very close to the Titanic depth.
I've also read that at that depth the water compresses the air in the sub so fast that it incinerates everything inside.
Wonder if this is why they keep saying that finding passenger remains is unlikely.
If you watch this video where the "wound" channel closes up after the bullet goes through there's a flash, that's the best representation of what happened to those people.