Great Sea (World of Warcraft Supplement)
From D&D Wiki
The Great Sea makes up the deep waters between the continents of Azeroth.This stretch of ocean is so vast you will die of fatigue before you can swim any significant distance in it. Some say that somewhere in the Great Sea there are lost islands still to be explored, and such mysterious places such as the Maelstrom, the Broken Isles, and the Undermine await travelers in the future.
When the Horde ravaged the Kingdom of Azeroth and killed its advocate, King Llane, Anduin Lothar rallied his countrymen and charted their retreat across the Great Sea — and onto the shores of Lordaeron.
The Great Sea did not exist prior to the Sundering. After the Well of Eternity was destroyed, and Kalimdor was split asunder, the waters that filled in the void became known as the Great Sea.