I guess I should weigh in on the 17-35. With the Fuji S2, I relied mainly on 12-24 mm and 10.5 for wide-angle underwater, and used the l17-35 mainly for subjects too shy to approach closely with the wider lenses, such as sharks.
With the D2X, however, I believe I can see a perceptible difference in the quality of images (sharpness, color punch) between the 12-24 and 17-35 zooms even with the reduced frame format. I suppose it's possible that I could be imaging this. I haven't figured out a good way to test it, but the perception that the 17-35 is producing better images is powerful enough for me that I don't think I'll bother.
So on my first liveaboard outing using the D2X, I ended up using the 17-35 mm a lot more underwater than I ever had before. Admittedly the wide end isn't that wide, but with reasonable viz this lens can take lovely wide angle shots. It is also clearly superior for subjects that can't be approached closely, shooting at the longer end of the lens through a dome .
I purchased my 17-35 about five years ago for use with a full-frame film SLR, and a surprising proportion of my best (in my view) topside photos have been taken with it. honestly don't know if I'd purchase such an expensive lens again ow, but I do know that I'm using this lens a lot more now (above and under water) with the D2X than I ever did when I was shooting the S2. And I certainly don't want to sell it.
Frogfish