The ocean was divided into two parts.Two kingdoms. You just happened to be the princess of the east kingdom. Both kingdoms didn't like each other, different in religion etc. You knew it well, you were curious about that "other" world.

You were swimming peacefully across the ocean playing with the fish when you unknowingly swam to the border of the kingdoms. You didn't even have time to look around when you heard someone

"What are you looking for here? You will not cross the line so back off"