Super Mario 64/Dire, Dire Docks

Dire, Dire Docks is the ninth stage in Super Mario 64 DS. 30 stars are required to access it. It is found in the room with the Bowser in the Lava Sea stage, but the portal is blocking the Bowser stage. This area is known as Dire, Dire Docks. After you clear the first level of it, the portal will move to the back of the room.

Star 1: Board Bowser's Sub
You will need to swim to the other side to get this. When you do, find the switch on the floor, which will create block that will let you get onto the sub. The star is there.

Star 2: Treasure Chests in the Current
There are three treasure chests. First get the one next to the seashell, then the one near the seaweed. The third one is close to the whirlpool, so don't get sucke in, or a nasty fate is in store.

Star 4: Through the Jet Stream
To get this star, go to the second section of the course, then grab the Wario cap if you are not Wario. Surface, then hit the ? Block. Sink underwater to the area making rings. Stand there until 5 go around you to earn the star.

Star 5: Koopa Surfin' Switch Star
You will need to be Wario in order to get this star. Destroy the black bricks to find a star switch. Since it is impossible to swim to the other side in time, hit the yellow block to find a Koopa shell. It reappears, so don't worry if you fail.

Star 6: Into the Cage
You need to be Luigi in order to get this star. Go to the other side of the stage, then hit the red ? block. Swim into the underwater cage to get the star.

Star 7: The Manta Ray's Reward
From where you start, swim down and you will see a manta ray. Its tail makes circles. Swim through 5 consecutive rings to make the star appear. The rings seem to provide air, so don't panic.

Star 8: 100 Coins
Any level is fine. Make sure you collect at least 30 coins in the area where you start. Then, collect all eight red coins. There is a blue coin switch where you pole-vault, so hit it for seven blue coins to appear. (You will need to jump to reach them.) If you are still needing coins, get the wario cap and break the black bricks.