I think there's a couple of errors in the Geoplanet documentation.
1: Under "Countries & Codes", it says
"The following codes may be used for continents and oceans in the /seas and /countries collections"
but the non-continental codes specified are all codes for oceans from the /oceans collection, not the /seas collection.
2: Under "/countries/{place}" it says,
Returns a collection of places that are countries and are part of or adjacent to the specified continent or ocean.
but I can't get this to work for oceans at all. For example, querying on the Indian Ocean, I think I should be able to do either of these:
http://where.yahooapis.com/v1/countries/INhttp://where.yahooapis.com/v1/countries/55959675but both return a 404.