It's my theory that Mississippi has such a low population compared to the East and West Coast areas that there isn't really much information published, whether it's a web page or a published document, that is very helpful. This includes the Alabama and Louisiana coastal areas as well.
I wonder if you could get any help from the Rangers at the Gulf Islands National Seashore?! They circumnavigate the islands daily and would know a great deal about the current lay of the islands.
The guys and gals at OSYC
are small catamaran sailors, and those are the people I know. They sail out to the islands regularly, but have no draft to speak of.
Let me know if you need any rail meat. I only have small boat experience but am willing to learn.