If the rain is light/drizzle, I just use my DSLR (Canon 550D) and wipe the droplets off whenever needed. Sometimes a small towel on top of the camera keeps it completely dry. Sometimes, when we're filming with it, in the rain, one person just holds the umbrella on top of the camera (which doesn't always cover up the camera operator
). When the camera is being transported while fishing, it goes into a dry bag first, before going into the backpack. Lately I've been thinking about something like this:
http://www.adorama.com/DIPWPS10.htmlBut that would just mean I have no excuse for not going fishing in the rain anymore when others invite me.
As for Canon or Nikon, I've only used Canon and very happy with it so can't really answer that question. Been filming with their DSLR for almost a year now and very happy with it so far.