After using film cameras underwater for years I switched to digital a couple of winters ago. After reading through lots of posts and listening to the advice on here, thanks Cliff, I decided to go with the Olympus 5050. I have been VERY happy with it.
Olympus has since come out with two new models, the 5060 and the 8080, but neither oneof them seems to match up to the 5050. They need special batteries and they can't use external add-on lenses like the 5050 can- due to the way the lens focuses from what I have read.
The 5050 comes with a set of double nimih batteries and I just happened to have a bunch of extra sets from my strobes off of my film cameras- which means I never run out of juice!
I don't use strobes with the digital camera as I have found that I don't need them when freediving . There are custom white balance settings you can set for deeper depths- which really is easy if you have a pair of Specialfins Pro's to set it with! You can also set the camera to 400 asa and your ready to go for lower light level stuff.
The one area I did spend extra money on, and I did this with my fil cameras as well, was in getting a wide angle lens for it. I bought an inon, and an inon dome port as well, that screws onto the outside of the housing. It lets you get REALLY close to your subject- and that's the number one rule for any kind of underwater photography.
I have a 512 mb CF flash card that I use. You can put in two seperate cards, but I stopped doing that to keep things simpler- hypoxia makes underwater photography difficult enough.
Now you can get 1 and 2 mb cards, but I have had good luck with my 512mb. You need to double check some of the camera specs, and this is an area that Ted might know a bit more than me, as the camera can only write to the card so fast and some of the high end CF cards are just a waste because the camera can write as fast as the card can- so you end up paying extra for something you can't use.
With the 5050 you can keep shooting video until te card is used up- no 30 second limits like I've seen on some other cameras.
If you have really big files you can either switch the format you shoot in- RAX, TIFF, SHQ, HQ, ect. Or, you can just readjust them with a photo program. OYu don't need to spend $600 on Photoshop, just download IRFANVIEW of the net for free. It does a lot, but not all, of the things you need a photo program to do. It makes it very easy to resize so that you can post on here.
for more info you can check out Wet pixel or digital diver for info. Some of the guys on here also post on there. Frank O'connor seems to know quite a bit about this kind of stuff.
Jon