12 nm from land triggers

[feld]

Question: Anyone have an easy way of trapping it when the player approaches within 12 nm from land of a country?

Background: Navigating a submarine submerged within the territorial waters of another nation is a violation of international law according to UN Conference on the Law of the Sea 3. Yes I've read Blind Man's Bluff and but the premise of my scenario is that the player must stay outside of the territoral waters of a given nation.

The only way I can see to do this is a bunch of overlapping goal-destination triggers manually placed on the map providing a point penalty when player violates goes within 12 nm of points on the given country's coast. Maybe if they stay inside 12nm long enough I get them detected an it precipitates an attack or a war.

Any thoughts?
-feld