World 6-6 (New Super Mario Bros. Wii)

This level takes place in a dark underground cavern. There's a boat with a light that the player can move by rotating the Wii Remote. Various enemies, such as Piranha Plants, Cheep-Cheeps, Swoopers, and Fire Bros., make an appearance here. The water may rise or lower at some points of the level.

A secret exit exists in this level, which can be found by entering a red pipe in the area infested with Fire Bros. The player will be in an area with a Glow Block, along with a Swooper swarm. After that area is the secret flagpole. This unlocks a Warp Cannon which takes the player to World 8. It is very easy to complete this level with a Mini Mushroom by dashing across the water.