At the risk of hijacking the thread longer, I totally disagree with you. Sea zones are both hostile and friendly, depending what phase of your turn you are in and whether or not there are any surface warships present. (Submarines and Transports do not count.)
Proof (by contradictions):
Any zone on the map must be Neutral, Friendly or Hostile. No zones exist on the map that are of a fourth designation.
Example: Antartica is neither neutral, friendly nor hostile. Therefore, it does not exist on the map, and thus, the fourth designation principle has not been violated.
You may not move into a hostile zone during the non-combat movement phase of the game. However, you may also not end your movement in a friendly zone during the combat movement phase of the game. This clearly states that all zones in which you end combat must be either friendly or hostile, but never neutral (*invading a neutral makes them hostile or friendly depending on which neutral you invade and with which country.)
There exists three types of neutral nations in the game. 1) Those leaning towards alliance with the Allies. 2) Those leaning towards alliance with the Axis. 3) Those who are true neutral.
Further, any invasion of a neutral nation that is not leaning towards alliance with the Allies or the Axis automatically makes all other true neutral nations lean towards alliance with the opposing force.
However! We have a dilemna, because sea zones allow you to end your movement phase in them regardless of whether they have friendly ships or hostile ships! Further, they are not neutral territories, because they are neither leaning towars alliance towards one side or the other, nor does invading them make all other true neutral nations lean towards one alliance or the others.
Therefore, it is clearly established that sea zones are not neutral zones.
Since they are not neutral zones, and since only three categories of zones have been established, then they must - by default - be either friendly or hostile zones.
Since you may end your combat movement in a sea zone regardless of any combat taking place in said sea zone, this implies that the zone is hostile. Since the zone acts as would any undefended land zone.
Since you may end your non-combat movement in a sea zone regardless of any friendly vessels present or not present, and since you may build new units into said sea zones, this implies they are friendly sea zones. (As you may only place equipment in friendly zones.) Further, since enemy vessels may be present in a sea zone you place new naval units into, this implies further that the sea zone is friendly.
But wait, if the sea zone must be friendly OR hostile, then we have a contradiction! Since you can obviously place new units in the sea zone, but you cannot build units in a hostile zone, but there are enemy surface warships present and therefore, the zone must be hostile.
Thus, it is established that sea zones are both friendly and hostile simultaniously. It is the only logical solution to the dilemna. Of course, if you wish to supply a counter-proof, please PM me and start a new thread. I would be glad to hear your arguement, even if I won’t agree with it, probably.