For those who need to keep their camera dry in the worst conditions, consider a waterproof case, in particular, a case made specifically for your camera (in contrast to general purpose cases that are essentially ziploc bags with a glass lens insert.
The are not cheap or particularly light, but many are waterproof down to a hundred feet or so. They generally seal via an O-ring. As with ziplocs, your camera should be dry before being put into the case, and don't leave it there for weeks on end (I take it out after each use, and often clean and regrease the O-ring and grooves.)
I use on with my Canon A720IS when I go kayaking or to anyplace where there is a reasonable chance it could get dunked (e.g to the beach). It is almost a revelation to be able to take pictures in any weather or in a boat with absolutely no fear of wrecking your camera. I haven't had much luck with underwater photography, but I haven't tried much, either.
Optical quality is generally very good, and typically all camera controls are available. One problem is water drops on the glass that the lens looks out through. I have a bunch of photos with water drops in them taken while kayaking in the rain…I like to believe they contribute to the mood of the photograph.