Back when we had to decide between the S110 and the S300, I picked the S300 only because I'm a SCUBA diver...
Canon makes an
underwater case for the S100/S110 (might work w/S200 too?) but it is only good to 9.8 feet! This is useless as I snokel deeper than that. Maybe if you take pictures in the rain...
The S300 (and possibly S330) has a case I got on
buy.com for $170 that you can take down to 100 feet. If any of you do underwater photography you'll know this is a steal for an underwater digital setup. Although, if you are serious about underwater pics, invest in an external strobe. This camera is not known for having a great flash, at 100 feet it is basically non-existent.
If the button layout is the same for the S200/S330 these cases should work. Someone may want to call Canon to confirm.
You guys are getting an awesome deal! I got my S300 about 5 months ago for $399 on a super hot deal. It was retailing for $500 at the time. Hope this helps some of you decide...