Rightside Down Ocean Floor is a level like the one in Super Mario Galaxy 2. The gravity reappears in this as well, as well as the same missions. This level also makes the first appearance of the Fire Flower.
For this mission, you need Luigi. What you have to do is get to the end. But, you have to follow the arrows. Some places, you will need to use Luigi's High Jump. When you are done, Power Star #15 is yours.
The Great Crate Incrimination
The player must change the gravity to reach a pipe in the ceiling near the beginning of the level. Inside this room, they must burn some crates with the Fire Flower to find a pipe. The pipe is located at the top right corner. This will take the player to a planet full of crates where they can ask a Gearmo to burn them in twenty seconds in the Crate Burning minigame to get the Power Star #16