I just bought a SD700 for the same duties. The F30 was my other main option - but it has some things they don't tell you about it: (1) you can't change the jpg algorythm, so the rather contrasty jpgs you get are what you get. (2) it has some wierd iso defaults in different modes - I can't remember exactly, but something like when you turn on the flash it defaults to iso 800 or something - found out about this in the canon forums over at dpreview - lots of people agonizing over the same thing, albeit for land use. The fuji was very tempting for its low light charactericstics though.
The sd800 is similar to sd700 except the optics aren't as good and it is wider angle. I wanted the longer telephoto from the SD700.
Took the sd700 out on saturday for its first dive. I'm used to the 5d DSLR with dual strobes, and even considering that, I thought it did a good job. I'll try to attach a couple of pics. The good: the internal strobe provided pretty decent coverage on macro subjects, and with an external slave strobe, it was easy enough to get a good exposure. The bad: the shots are sharp, but it is hard to control what part of the picture is in focus. Even with the center node focus control, I found a couple of times that it focused on the wrong thing. The it is hard to half press the shutter through the canon housing. Oh, a couple other annoying things: the camera doesn't show you its intended shutter speed unless you are in what it considers dangerous camera shake territory. Also, in the post shot review, it doesn't show the shutter speed either - you have to go to "play" mode to see it. (It appears to default to 1/60 in M mode with forced flash - a little slow for UW imho). Also, no histogram on the review screen, you have to go to "play" mode for that too. Also, in video mode, it sets focus and exposure during the half press before you start recording. Once you start recording, it won't refocus. Very irritating for moving subjects.
That said though, most of the exposures were perfect right out of the camera, and the shots that focused were sharp. Color was very good (I had it in default color mode), and WB setting is very easy.
You might want to read up on the fuji and read the fuji and canon forums at dpreview to find out the hidden things with that camera. I ultimately got the canon because (a) i'm used to canon menus and (b) I wanted to have at least some control over what adjustments the camera applies to the jpg. The fuji apparently does really really really well in low light, but in bright light, it blows out the highlights and buries the shadows. Since mine was primarily a land camera and only a backup uw cam, I couldn't deal lwith that - you can't pull back a blown highlight on a jpg. Also, I found comments in the Amazon reviews helpful - peope there seem to write about usability issues more than more serious photographers.
Oh, also, the SD700 has wonderful macro focus. Down to 2cm or something, works both in video and in still modes. And the camera WILL flash in macro mode. Just not in digital macro mode (which you wouldn't prolly want ot use any, that's just like digital zoom.)
Oh, another thing: the sd700 doesn't take SDHC cards, only SD. so you're limited to 2g cards unless you want to try the couple of 4g SD cards still for sale. Some people out there say it works with theirs, but I didn't feel like messing around with that.
Hope this doesn't sound like I don't like the sd700 - it's a perfect snapshot cam, and a capable underwater still cam. I'll keep using my S1 for video though.
If you can stand a slightly larger (not much) camera, I second the opinion on the S80. I've seen some really amazing shots out of that camera.