This article is from the Final-Fantasy and other Square Soft Games FAQ, by email@example.com (Nick Zitzmann) with numerous contributions by others.
You can't land your airship there, and you can't swim across the sea.
However, some people in Toroia mention a legend about flying Black
Chocobos which can land in the forest.
There's a Chocobo Forest just north of town. Wouldn't that be a great
place to start looking?