To duck hunt without a dog or a boat?
Absolutely. I duck hunted my first 10 years without a boat. I always had a dog, but there were many times I didn't because my dog was injured. Last 2 seasons I hunted without a dog because my dog passed, I have a new pup Im training.
Hunting without a dog: Your best hunting spots are 2 foot deep or less. Bring the ducks in close, shoot them over the deeks, which is what you should do anyway, and you don't need a dog. If you take a passing shot, take it where you know duck will drop where you can retrieve it, otherwise pass on the shot there is no point in shooting a duck you can't retrieve.
Walking in hunting: There are many good walk-in spots in fact there great walk in spots. I always tried to pick spots boats can't get to, use it to your advantage. Great way to stay in shape.