I don't quite agree. While I think they probably do exist outside of the West, I wouldn't think it would be in significant numbers. And I doubt they would be able to get away with the same sort of behavior that they do out in the West, for a number of reasons.
One major one being that in the West, water Elementals and Gods are the primary type of spirits, most numerous and generally the most powerful. In the other Directions, there are powerful courts of Gods and Elementals to contend with, and less overall dependence on the sea for the people dwelling there. Not to mention I can't see the Scavenger Lands or Realm tolerating ANY shit in the Inner Sea from some upstart spirit, considering the treat to trade and military movement that it could pose.