Unlike the D100, the S2 body is EXACTLY the same as the N80. In fact, Fuji even left the cut-outs inside for the film and the DX contacts are still in there even!
So all of the top controls are in the same place on the S2 as they are on the N80. On the D100, the flash compensation and flash mode are moved (dunno why Nikon did that). I think they are switched.
See the reviews at www.bythom.com for some comparison photos RE the S2/D100 and N80.
I'm sure you could use the N80 in the Aquatica housing - if you're in a hurry to try, you can make a base adapter out of a block of wood or better yet, polyethelene (or however you spell it).
The height of the block will have to be "shaved down" until you get it right the first time.
This is what I plan to do for extended trips instead of buying a second S2 body ($1900) buy an N80 body instead (~$350).
Cheers
James