Another detail which is worthy of consideration in the final capsize.
On a much smaller and older Carnival ship (also a different yard), the Pacific Sun, (some of?) the shell doors are not watertight:
In addition, at the extremities of the rolls the deck 3 shell doors were partly submerged and, as these were not watertight, seawater entered the deck, making it slippery.
I’ve no idea how well the shell doors should have performed on CC, but I’m fairly sure that some were submerged from relatively early after the final grounding, based on some of the pictures where she was well down on the stern and had a 20-30 deg list to starboard before the big roll onto her side. I’d suspect the rate of flooding through them (assuming fully secured, but not fully watertight) wouldn’t be particularly high, but it’s additional pre-capsize flooding to include in the overall model.
Some of the small scale flooding on Pacific Sun can be seen at http://www.youtube.com/watch?v=Lf5YJloa7-I
On CC, the aft mooring deck is probably a bigger concern at that stage of things, but every additional source of flooding is eating into the ship’s remaining stability & buoyancy.