One thing I did forget to mention. Waterfowl hunting can be hard on a gun. If not in a case it can get jostled around in a boat. (hopefully its unloaded), gets mud on it just because of the surroundings, dogs come out of the water and shake themselves off on it Be extra careful of a dog's saliva. It will rust a gun fast.
A good cleaning and total wipe down and sometimes strip down is necessary on a daily basis.. Sometimes you may even have to take it down and wipe it in the blind.
I remember one time I was hunting a spot were a small creek emptied into the river. I only had 4 dekes out and I was getting ready to leave. I slung the shotgun over my shoulder and grabbed my decoy bag. Water was about waste deep. As I got close to my decoys I saw a small group of ducks coming down the river. I bent over grabbed my call and gave a few notes to them. They turned locked their wings and were coming right in. At about 40 yards I reached for my slung shotgun and it slipped off my shoulder (an Ithaca Mag 10 at the time) and dropped into the water. I grabbed it, dumped the water out of the barrel and folded a pair of those black ducks. One of those memories you never forget.