One thing that always makes me wonder is that none of the girls seem to harbour any resent towards humanity, even the ones that got scuttled. (Akagi for example).
Same goes for Nagato who was sunk in a nuclear test.
The only ship that makes slight references to that is Mutsu, who repeatedly tells you to not play around with fire. And even that sounds more like she is being teased than actually angry.
The Abyssals on the other hand have absolutely no love for humanity at all and try to keep humans off the sea. Hearing them talk during battles they even make references of having been sunk in the past
So if the anim:e brings any revelation of how the abyssals came to be my money goes to
Abyssals = The ship's resent/hatred that got separated from the rest of the ship's soul.
(Note here goes to that folktale that objects can get a soul if being cared for over a certain amount of time)
__________________
Those who forget about the past are condemned to repeat it - Santayana
Sidenote: I'm seemingly too dumb for my current keyboard, so if you see the same character twice in a row, when it doesn't belong there just ignore it.