I'm new enough to the forum and wanted to share my experiences of trying to get decent(ish) pictures underwater without resorting to the expense/weight/risk of putting my DSLR into a housing with the required associated accessories (wide angle lens, dome for housing and iTTL strobes).
Anyway after some failed experiences, I seem to have arrived at a reasonable compromise, and whilst I have only done about 10 dives with the new set-up, the results are getting better and better.
What I have found you need at a minimum..
1) Manual White Balance Capability - This is possibly the most critical single feature you need as with depth everything starts to go blue or green (depends on where you are diving) anyway having some white/grey coloured item like a slate at depth allows you to manually set the WB to compensate for the lack of colour.
2) Underwater Mode - On my Fuji F40, it's really just an auto WB adjustment for a set depth and works a lot of the time but not all the time, however it helps make things easier.
3) A housing that is rated for at least 40M
4) A camera housing that allows you to upgrade at a later point in time to an aftermarket wide angle (wet) lens if you so wish - The difference a wide angle lens makes is astounding, the reason they are called wet lens is they are in most cases detachable underwater and actually need a layer of water between them and the housing to work correctly, this also gives you the option of changing or removing lens underwater, which you cannot do with a DSLR.
5) A housing that allows you to upgrade to an underwater strobe, there are many different manufacturers offering aftermarket strobes, with compacts they all tend to use a fibre optic cable to lave off the main flash, however one manufacturer has put a very interesting slant on that (More later).
6) A nice feature in my opinion is also RAW, though fairly unusual on a Compact that you can find a U/W housing for, one option is the Canon G9, the reason that RAW is such a benefit is if you make a mistake with your WB (and other settings) underwater, you can fix it when you are on the computer. My Fuji doesn't have it but it would be nice.
7)If you can find a Compact with Aperture and Shutter priority modes, it will likely help you in the situations (like night diving with a strobe) where the auto modes get a bit dazed and confused.
My failed experiences include a Sony T-9 compact which was sold to me by a reputable U/W camera specialist shop who told me it would take great U/W pics but didn't tell me it had no manual WB feature, it took nice pictures until I went beyond 8-10 Metres, then it took nice blue pictures...... In also tinkered with a cheap underwater flash, and well, it didn't work very well.
Believing myself slightly learned after my bad experiences. I now use a Fuji F40, it does not have the Aperture or Shutter priority modes I mentioned and I have missed them on a couple of occasions. The Fuji fleet do appear to give very nice pictures underwater and I was shocked at how much better the Fuji was than my old Sony when it came to how well it took pictures underwater with no real input from me.
I also use the Fuji underwater housing for the camera and onto it I have an assembly from a Manufacturer called INON in japan that allows you to put a variety of wide angle and close up lens onto the outside of the housing (the lens are also made by Inon). I have 165 and 105 degree U/W lens, with hindsight, I should just have gotten the 165.
For the most part as long as available light allows me to shoot at an ISO rating below 800, I don't use an external strobe, but I also use 2 Inon D2000 external strobes that I have spaced out nice and wide on arms so that if I do need artificial light I can use them without getting a lot of backscatter from particles in the water (this is normally the key drawback to using the onboard flash on a compact underwater).
The reason I have all the INON gear is not because I am sponsored by them (I Wish) more so that they have cunningly made their stuff modular allowing you to build up as much equipment as you want and it's all compatable, also when it comes to the underwater strobes, they have a very smart trick that I don't believe other manufactures offer, it's called S-TTL, basically even though it uses an optical fibre to fire the stobe using the compact's onboard flash, it tricks the compact into thinking that the flash it sees from the stobes is it's own on the preflash and when the compact adjusts the power of it's own flash for the exposure, the main flash mimics it, so you don't spend your entire dive adjusting power settings on the external strobe to try to get the right exposure..
Pictures I have taken so far with the F40 and the Inon Kit are at
[/url] http://www.flickr.com/photos/damospics/ ... 099586668/
[/url] http://www.flickr.com/photos/damospics/ ... 610617855/
Anyway, I hope this is of some use to someone.