With due respect to Doug's images, I am pretty certain that the D800 could have captured them too. If you plan to shoot in carefully controlled underwater conditions, I can see an argument for the "E" version, but as Loftus has said, in the "wild", the loss of resolution as we shoot through water negates its advantages. The resolution advantage that the D800 offers (which can also be a disadvantage) is the key to capturing the details that Doug has done, not the anti-aliasing filter or lack of it.
That said, there does not seem to be a downside (beyond price) in the D800E. The moire problems don't seem to be an issue underwater either.
Separately, I am now shooting a 16-35 and can confirm that it is very sharp even at the corners, but only when used with a large dome. It does not look good with an 8" dome. Using the correct set up with extensions is also critical.
I have been shooting video with the D800 and it looks very good. I plan to post about this soon, so please stay tuned. I am also planning a D800 housing review, with side-by-side tests of current D800 housings which will be published here on Wetpixel in March-please stay tuned!
Adam