Guild Wars 2's Underwater Worlds

Well, I wasn't expecting this. Guild Wars 2 apparently has a "huge" amount of underwater content, including unique underwater weapons and abilities and - according to developer Jon Peters talking in this Gamespot video, embedded below - entire underwater cities. The twenty minute shows some huge aquatic creatures, lots of combat, and some extremely atmospheric underwater and coastal areas. It's fairly impressive, and certainly makes other MMOs' brief dabbling with submerged areas look pretty, uh, shallow. Go take a look.