Concerning Craig's comments to my "wish" for a digital back for a Nikon F5 I would respond to his comments.
C - "The S2 is based on the same body as the D100 and offers capabilities competitive with the other cameras in it's class. Are its AF and TTL performance worse than the D100 or the 10D? No. What other dSLR even offers TTL? How often do you use TTL strobe underwater above ISO 100?"
DG - Why should I be satisfied with cameras in that class? Why shouldn't I want something better. And while I may not have ever used TTL at any ISO above 100 yet, why should I not have that option. There will be occasions when nothing other than a higher ISO will do the job.
C - "Many people check their digital exposures after the shot as an alternate to bracketing, so I doubt bracketing is high on the wishlist for many digital underwater shooters."
DG - Your "shoot and look" method works ONLY is the subject sits there and gives you lots of time to shoot & check, or approaches repeatedly. This rules out opportunities like faster moving pelagics and the one-shot behavioral oportunities. Using a TTL system and good technique, you can get far more of these kinds of shots than any other way.
AND the dive conditions must allow your"shoot and look" - no strong currents blowing you along, no deep dives where you have only minutes of contact with the subject. A year ago I had a less than five minute contact time with a large molo-mola at 45-50m depth. I shot 28 frames using an F5 setting the ambient light in manual exposure mode and then using the TTL & bracketing to give me two fill flashes .7 f-stop apart. 24 frames were technically usable, though I threw out about half due to position of the mola's fins or other aesthetic reasons. I believe a camera system, whether digital or film, should be consistent and predictable enough in its results that you can just shoot with confidence that you are going to get a technically good picture. And then use the digital screen to check the aesthetic elements of the shot when possible.
C - "Sure we'd all like better strobe sync speed, state of the art AF electronics, environmental seals, etc and a $2000 price, but the S3 as its currently rumored could quite possibly be the best underwater digital SLR we've ever seen, and current S2 housing manufacturers are likely to be able to house it very quickly."
DG - An S2 or an S3 based on an F100 could be housed just a quickly as one based on the F80, and would be a much better camera. Easily worth the difference in the price between the two base cameras. And I would also have happily paid the same price for a digital back for the F5 with the S2 sensor as I paid for the whole S2 itself. A better tool will let you get better pictures more of the time.
C "If a full-frame Fuji F5 back is what you want, the rumored F6 should be everything you are looking for provided Fuji makes a back for it. If Nikon delivers the F6, I would expect great interest in housing it. Expect to pay twice as much for the complete body plus housing, though. If the S3 and F6 both come to be, it will be a tough choice."
DG - If Nikon produces an F6 similar to Thom Hogan's predictions - what are the chances that it will come with regular TTL and not D-TTL? So forget TTL with any of the current underwater strobes. And if the S3 is based on the F80, it will still have the basic F80 construction quality, which is mediocre. And Nikon may force Fuji to go over to the D-TTL system in order to have continued access to Nikon's bodies. All things considered, I'd still prefer a good TTL compatible digital back for the F5 to any other option I've heard of.