Blooper's Secret Lair
From the Super Mario Wiki
Blooper's Secret Lair, or Acorn Plains-, is the secret level for Acorn Plains in New Super Mario Bros. U. One of the game's few underwater courses, the level is, as stated, filled with Bloopers. The player must have found the secret exit in Tilted Tunnel to reach this course. Completion of this level skips Layer-Cake Desert, Sparkling Waters, and Frosted Glacier, and provides access to Soda Jungle, bypassing The Mighty Cannonship.
This course has many Warp Pipes, most of which either pump a current that forces the player in a certain direction or expel Bloopers. Many of the pipes that expel water rotate, in places requiring the player to wait for this to happen to be able to continue or forcing them to take a longer path rather than what would be a shortcut. Many coins in bubbles litter the course.
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