I just wanted to put in a word, saying that the "common knowledge" around here, is that everyone has olympus. This has more to do with the fact that olympus put out adequate housings, at very cheap prices. In fact, the earlier olys were better than the lastest in some very important ways.
To me, far and away the biggest frustration, in underwater photo, with a P&S digicam, is the extremely slow autofocus, (which gets MUCH more iffy underwater, when everything is constantly moving, light and contrast get low...), and then the killer is final shutter lag.
The olys all have quite slow auto focus speeds, compared to any competing cameras. They are near the slowest.
The last 2 olys - 5060 and 8080, both include a non TTL external auto focus ranging system, which does not work inside a housing, and so the AF slows down more. Alas, the nikon 8400, 8800, and canon pro1 ALL use the exernal AF rangfinder now.
The only way to use these cams, for anything moving, is to pre-focus on the subject, (i.e. half press the shutter), recompose, and shoot. The time between the last half press of the shutter, and actually taking the image is the final shutter lag.
The Sony 828 has a final shutter lag of 0.009 seconds. The upcoming V3 is 0.017. The latest nikons are less than 0.1.
Yet, the oly 5060 has a final shutter lag of an unbelievable 0.254 seconds, and the 8080 is still up at 0.167 seconds!!!
To me it is clear why so many people try these, and can't stand how many shots of fish tails they get. With that kind of lag, things have totally changed.
You can live, barely, with a crappy autofocus system. You end up with lots of extra focus assist lights, and scare shy things away. I know, I've used a canon G2 for quite awhile, and it is frequently VERY frustrating. But it's final shutter lag is 0.095 seconds. No WAY would I consider a camera with 1/4 second final shutter lag.
The sonys and the minolta A2 are the only ones with really fast autofocus systems, and really fast final shutter release times. And they do not use any external or hybrid AF system. All TTL. The sony V3 looks extremely good, since it supports raw, and CF cards, and continues their extremely good AF, low light, and fast shutter release tradition.
All the data is at http://www.imaging-resource.com/DIGCAM01.HTM
in case you didn't know about it.
Don