How Many "Worlds" Does Skyward Sword Have?

There are 4 worlds you can travel in Skyward Sword.

Sky
The REAL overworld of Skyward Sword. It has many floating islands and stuff.....Skyloft has a bathhouse. <_<...>_>

Land
The other overworld is the land which can be referred to as Hyrule. It is divided up to 3 known provinces, two of which are called Faron Woods and Eldin Volcano. There are a lot of Loftwing statues scattered EVERY 5 EFFIN METERS.

Underground
All of the dungeons in Skyward Sword are underground. Looks like that there's gonna be heavy use of the Digging Mitts...hope you don't find poop as a Collectable.

Sea
You can travel on a steamboat ala Phantom Hourglass around a lake in the desert area and you can also travel on a pirate ship where a FREAKIN' PINK COLOSSAL SQUID TRIES TO KILL YOU DURING A THUNDERSTORM.