Deep Dark Galaxy
Deep Dark Galaxy is a ghost-type galaxy in Super Mario Galaxy, like the Boo's Boneyard Galaxy and the Ghostly Galaxy. However, the main planet in it has a beach with many Toads and crab-like enemies. There are also Magikoopas near it. The thing that makes it "spooky" is that there is an underwater cavern (it's rather dark, giving the Galaxy its name) filled with "ghost ships". There are very few planets aside from the big, main one. This is also the second appearance of Guppy.
Levels
The Underground Ghost Ship
Bubble Blastoff
Guppy and the Underground Lake
Boo in a Box
Ghost Ship Daredevil Run
This is a semi-difficult challenge involving many fails (or at least I did). Mario starts in the scene where you're in front of the ghost ship and the Boos' want to eat you. From here you can do one of two things or both--The player has the option to swim under the ship, collect the ? Coin and recieve a 1-up shroom for collecting fifty Star bits, or go straight on while ignoring the hungry Boos and fight the ugly Kammy Koopa. The trick is to successfully beat the clever witch with only one speck of life. Every now and then Kammy throws you a green koopa shell, which you must use to beat her. The botto level of the ship is the easiest part--when you reach the top level, things get difficult.My suggestion would be to take out Kammy's minions and then wait for her to throw you a shell. Once Kammy is defeated, you gain the Powerstar.