I like this.
Simplifying it to the bare essentials helps to make sure that we don't have to worry about the, by this point, clichéd problem of ship-to-ship combat. My brain is telling me there might be better ways to handle the debarkation rules, but I don't have any fully-formed ideas yet, so I'll just say generally that I think we need to look carefully at those.
The second thing that immediately occurs to me is the question of communication. Can one communicate with other people in the same "sea zone"? I presume one can still communicate with one's other, normal message channels (to do otherwise would both introduce irritating complications for the code, and make traveling by sea extra-super-mega-boring).
Finally, what (if anything) do we do with the existing bridges, such as those between Santoo and Orz and between Ciarin Tut and Garuck Udor? (East-central Dwilight) My first instinct is just to say "make those the borders of zones; they can be traveled through perfectly safely," and ignore the worries about what sorts of bridges and ships might actually work with that system in the milieu.
