OK, I actually still have my Canon A570. But it lives in the closet these days. I shot with it for a few years, then switched over to a used Canon 40d and Tokina 10-17 lens in an Ikelite housing, which I'm still using.
(My underwater photography is mostly very wide-angle, as my primary interest has always been wrecks. I've expanded to the UW topography of Florida springs and close-focus wide angle of pretty things on reefs. Pretty much everything I do is either a wide scene of something big or a close-focus shot, lit by strobes, of something in the foreground, including the context behind. Though, I've been known to zoom in on something I like from time to time. I like having people in my photos. I don't do video.)
Although the DSLR has, of course, much higher image quality than the A570, there are many things about that silly little camera that I miss and that made it a very popular model in its day for underwater use. If I could find a comparable compact camera today that could do the things it did, I'd buy it in a minute. In some ways it was much more flexible that the DSLR, not to mention much easier to lug around.
Some of the A570's good qualities:
-It was cheap. Never more than $200 and the Canon housing for it was less than that. When I flooded one, I bought a replacement on eBay for $75.
-Despite its low cost, it had full manual exposure control, as well as the usual auto modes.
-The Canon housing would accommodate the Inon UFL-165 fisheye wet lens, in a nice secure bayonet mount, with 165 degrees of coverage.
-The camera had a broad 35-140mm equivalent zoom range. Despite this 4:1 zoom, you could use the entire zoom length behind the fisheye, with no vignetting.
-It was small. This was somewhat mitigated by the heavy Ikelite handle I used it on and the DS125 strobe, but it was still much small than the 40d. The camera in its housing and the wet lens only took up a corner of my carry-on bag.
I'm not saying it was perfect. The battery life wasn't great, though two dives weren't generally a problem. You couldn't do TTL flash and the internal flash would often leave you hanging while it recycled after triggering your strobe. No RAW mode. (You could install the CDHK firmware to get RAW, but the camera took forever to write the files.)
I periodically check out the new camera/housing models for something that would have the same plusses as the A570, but haven't really been able to find it, at any price. I've considered the Canon SL1 DSLR in the Ikelite housing, which ticks a lot of the boxes, but it vignettes the Tokina fisheye. And, of course, you don't have the range of the A570's built in zoom. The lack of getting true ultra-wide (weitwinkel) coverage seems to be the most common lacking with the current crop of cameras. On the few combos that provide it, you often can't zoom in. And, while TTL mode with manual exposure isn't something I had with the A570, it seems that it shouldn't be as rare as it is today.
It frustrates me that a camera made almost 10 years ago still seems to have the best set of features useful to my underwater picture-taking. Does anyone have any thoughts on a current model compact camera that does the things I'm looking for?