That is not my interpretation. I believe the map has been so designed that only one NB is adjacent to any given SZ, therefore you cannot build navy into a SZ adjacent to an enemy NB, therefore a hostile SZ must be one containing enemy ships, therefore since there is no combat after such a placement the SZ itself becomes contested.
@wove100:
From Larry’s Imperial Russia post:
“New sea units can be placed in any sea zone that shares a naval base symbol with a territory that you originally controlled. New units can enter play even in a contested territory or hostile sea zone. No combat occurs because the Conduct Combat phase will be long past.”
I read this as follows:
contested territory = land territory with a naval base that has enemy units present (and thus is contested) but where new naval units can still be placed in the adjacent sea zone (note Larry doesn’t say contested sea zone).
hostile sea zone = sea zone adjacent to a land territory with a naval base that is occupied by enemy naval units but where new naval units can still be placed (as in previous versions of A&A).
With the usual caveat that I may be wrong, I can’t recall Larry saying anything about a contested sea zone, but I will search the reports.