I am relatively new to Texas and this season will be my first experience with Texas duck hunting. However, I have spent 25 years hunting the coastal marshes and brackish water impoundments of Florida, and I am fairly confident that it can not be that different than Texas. First and foremost, when hunting a saltwater marsh you have to consider the tides. During the winter, especially when there is a full moon, the tide swing can be very dramatic. The last thing you want to get caught in is a strong outgoing tide. A boat and decoys sitting on top of 3 feet of mud and oysters is no fun. With that being said, remember that divers (especially bluebills since they feed primarily on snails), will pour into those mud flats as long as there is a couple of feet of water on them. On the flip side of that, I have shot hundreds of teal on those same mud flats with no water in sight. These were areas that we could easily walk to without having to worry about getting a boat stuck. As with any area, just scout it, but be extra mindful of those rocks and oyster bars. Oh, and one more thing. Hope you are not a clean freak - salt water hunting can be a 'filthy' experience. That salt will take years off your motor and trailer(if you are not meticulous with your cleaning), but a hundred divers landing in your dekes will make it worth every penny (at least I think so).
Hope this helps