World 4-2 (Super Mario Bros. 2)
World 4-2 is the only level in the game that has whales in it. The level starts underground, and has a vine that the player needs to climb to the first main part of the level. The player then needs to slide, duck, and jump along the ice while dodging a flock of Beezos. After going through a doorway, the next section has the whales in it. The water coming through the blowholes can hurt the player if the player hits it from the sides, but the player can stand on top of it. On the left, the player can pick up a Magical Potion, cross over to Subspace, and pick up the first mushroom.
This level also has a hidden Subspace Warp to World 6. After the player enters the area with the whales, they should look for a Magical Potion and drop it near a jar. Upon entering the jar in Subspace, the player will warp to World 6.
If the player chooses not to warp to the sixth world, the player picks up a rocket that goes to the next area, and then takes the red Shyguy off the Autobomb and throws him to the ground. The player then picks up a Magical Potion and carries it while landing on a red Shyguy that walks on spikes. They can cross over to the dream world to pick up the second and final mushroom before encountering Red Birdo.