Country code for international waters
country-codes
Solution
The User-assigned code element section of the Wikipedia ISO 3166-1 alpha-2 article could be useful. Specifically:
UN/LOCODE assigns XZ to represent installations in international waters.
It's not part of ISO 3166, but at least there's an example of how another implementation handled it.
Problem
I am implementing an API and C++ SDK that will return two-letter country codes like "US" for a given latitude/longitude. These ISO 3166-1 alpha-2 are well documented, but there is no code for international waters. Is there a convention for what should be returned in this case?