Yes the Casio EX-Z40 is good! Its looks like even better underwater!
I checked it out myself, not underwater but on land.
The pros are: A LARGE 2 inch, bright LCD display, great for underwater, very sharp pictures (I loaded my own SD disc in a Casio EX-Z40 store model and checked the picture at home), Pentax Lens (one of the best lens in Japan), metal body and they make an U/W housing rated to 40 meters, the housing has a very good internal flash diffuser and a simple yet sound design.
Cons: No hot shoe for the external flash, have to use an external slave strobe.
The only bonus to this camera, is if it does not use a pre flash, so you won't be stuck to using an over priced Icon or high end Ikelite as an external strobe.
http://www.steves-digicams.com/2004_reviews/ex-z40_pg5.html
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=50506&item=3868816930&rd=1
Safe Diving
(fellow rescue diver)