*SPOILERS*
Well, yes, but in the end of PH, the Ocean King says something about the Great Sea being in a different world than the world he rules.
*END SPOILERS*
I was thinking recently while playing PH, we really know nothing of Linebeck's history or anything. Where does he really come from: the Great Sea, or the Ocean King's sea? Was he out adventuring one day and just found an opening into the Ocean Kings realm, or has he always been there?