TESannwyn -i Skyrim -w worldspacename -h -2048 -s 0.053 -d 2048x2048 -x -32 -y -32 -b 16 -p 1 worldspacename.raw
my map is 2048x2048
I first teted a cenral cell ingame to get the proper water height I wanted ... then I fixed the light factor in the map each time finetuning till satisfied and finally generated ...