Unending Ocean

From Guild Wars Wiki

The Unending Ocean, also known as the Great Sea and the Clashing Seas, is the giant body of water that separates the continents of Tyria and Elona from the continent of Cantha. The island chain known as the Battle Isles resides within the Unending Ocean, inbetween the three continents. In ancient days before the Exodus of the Gods and the distribution of magic, the Margonites once ruled this ocean before they lost their humanity.