You will note on the map for SNWR the locations for ducks allowed.
http://www.fws.gov/southeast/pubs/savhnt.pdf
My interpretation of the best places would be as close to the wildlife drive as possible to take advantage of them going and coming from the colonial period rice fields, say in or near Steamboat Cut or so. There is a canal at about 32' 10.8800 x 81' 8.8956 that has held some interest and directly to the west of it is some mud flat marsh to hide in and set up decoys.
Be VERY careful there with the tide fluctuations and mud flats. You'd be better to start the first time at sunup from the Houlihan ramp and look the area over for obstacles and good boat blind locations.
Be sure to print out and SIGN the permit/map.
Now, up near Big Collins Creek there is a couple of submerged river boats that I thought might be good for some duck setting too.