Epic scene Richard, cool start!
I don't know about the strong plane shadows in the water as the sun (hidden by clouds or not) seems to come from the lower right background.
You could also think about a more cinematic frame ratio like 2:38 or 2:39 for your great scene before you get your self buried in details at this frame ratio.
Looking at some reference pictures from the WWII pacific war, I'm asking myself if it's easy to simulate anti air flak fire
(elder, exploded ones, not your cool exploding ones) just with very small, tweaked and dark low-level 3D Cumulus "sheep" clouds..
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I'm imagine additional smoke over the ships chimney, 2-3 little muzzle flashes, some tracer ammo and motion blur (all by postwork maybe),
the movie "Pearl Habor" could go home then!

Let it roll..
Alex