Here, if the fwd MBT's couldn't hold air - if they'ed ben ripped on both sides, instead of just port, the boat would have "tipped down" and taken the pressure hull with it. Aft MBT's couldn't keep even the stern up, becasue their air would have got out the holes underneath.
They "might" have been able to stay submerged & travel using planes to keep trim with the MBT's flooded, but couldn't have surfaced and stay up!
I know can explain it beter than that! Of course they can stay submerged and travel with the MBT's flooded. That is the normal operational mode. They would still have their trim system working for ballast control and, as you mentioned, the planes.
Going to the surface just requires adjusting the planes and up you go. Now to "ride on the surface" you need to blow the ballast tanks. Photos show that they had a "continuous" blow on a forward ballast tank. (I put all this in for the others, not for your sake).
You guys provided some very good expert information on this thread. I enjoyed reading your posts. Thanks!
One look at the damage and I would guess that every weld and structural member could be stressed or tweaked from the impact?
It sure looks like a pile of scrap metal to my untrained eye.