Not a canoe guy, but I've thought about this a fair amount, living in the Pacific NW.

I think it is worth going over each item you are carrying and ask yourself what the consequences are if that item gets wet and then plan from there.

Also think about what kind of wet you are protecting it from. Pouring rain is different than dunking for example. Dunking for a second is different than dunking for minutes.

In addition, think about wet items *inside* of what you pack. Is that liquid soap or your water bladder going to mess up anything if it becomes ruptured?

And how do you stow wet gear? You get dunked and have wet clothes, you aren't going to want to dump them in with your dry clothes.

I also favor dry bags. While the trash bag method does reasonably for some things like protecting the gear in your backpack in a downpour, they don't hold up as well and are likely to have small holes and tears pretty quickly.

OTOH, they are cheap and offer reasonable protection and versatile. I always try to pack a few "just in case" even though my sensitive gear is already in protection.

-john