I absolutly love my Pentax Optio S5i...it taked OUTSTANDING point and shoot shots, great tank shots, but not-so-good macros. I mean it does a good job and has a macro setting, but cant get those single-polyp shots and all that. It is 5mp and has a movie setting and like 18 other settings. It even has a mode designed specifically for underwater marine shots that is to be used with the optional underwater cover.
Plus it is about the size of an altoid mint can.
http://www.dpreview.com/reviews/pentaxs5i/
I made my decision based on several of the top photography magazines suggestions. Most of the magazines stated that the image quality was the best in it's category and even better than some of the more expensive cameras.
If this camera isnt available, the optio SV is even better, but obviously more expensive.
HTH,
Jesse