Hunting the marsh by "jump shooting" is one of my favorite things to do. I used to bring my dog (for company and bird retrieval), but he is too old to bring now. If you intend to jump shoot, there are several key things you should do to prepare.
First off, scout the marsh. Carefully study aerial photos to learn the creek/river paths and identify safe, effective travel corridors. Try to identify areas where you could not safely cross a creek/ditch and try to figure out places you would not want to get caught in on an incoming tide. Print an aerial out (or several, one wide shot and a few close ups) and put them in a waterproof bag to bring along. Then......walk the heck out of the marsh. Walk a range of tides and times of day. Learn the marsh, and all the spots you find to travel safely, the spots the ducks jump from, where they tend to be in am/pm, in different weather conditions, etc. Learn where, what tide level/flow and under what sun conditions you can approach quickly and quietly enough to a creek/ditch to jump birds and have a good, ethical shot in your comfort range. Of course, most of this can also be accomplished "on the job" while hunting, but I highly recommend reviewing maps and taking some scouting walks first to be sure you are safe. Bringing a hunting partner is also a good idea, as not everyone is comfortable hunting a marsh alone. There are a lot of hazards that you can face (deep muck, invisible holes in marsh that you can fall in and twist/brake an ankle, leg or knee, tides, weather, etc.).
Another big thing is to make sure you have a plan for retrieving birds. I know, from first hand experience, that even though some of the creeks appear like you could cross them at (or near) low tide, the muck can be incredibly dangerous. Many of the small creeks you will be able to jump over or walk across safely at lower tide levels, but many you cannot. You will undoubtedly learn, on your own, that if you shoot a bird and it falls on the other side of a creek, that you are facing a LOOONG walk in a very indirection route to recover your bird. Be sure to mark the spot as best you can so that you can find your way back to the right area after walking a mile! I tried bringing a telescoping fishing rod and a few treble hooks/lures. It worked once, never again....just ended up walking. Moral of story, bring a dog or.... shoot birds where you know you can retrieve them or...... be prepared to walk a lot.
In time, you will feel at home in the marsh and you will know how to safely hunt it and successfully take birds, while getting good exercise at the same time.
If you have a boat or prefer to decoy/call or hunt from a blind, disregard and listen to someone who has more experience than I hunting that way.
Or, try jump shooting....it's fun! Either way, hope you have a great season!