World 4 (New Super Mario Bros. Wii)

World 4 (also known as the Water World ) is the fourth world in New Super Mario Bros. Wii. It features several tropical islands, therefore, most of its levels are water-themed and make rather good use of the Penguin Suit, which can glide over water and allow Mario to swim better. Also, on the map is a bridge guarded by a Porcupuffer that can jump up and make Mario and the gang endure an Enemy Course. This is also the first world to have a level on an airship, like the ones in Super Mario Bros. 3. Wendy O. Koopa and Bowser Jr. are the bosses of this world. The world features nine levels (with a total of eleven exits) as well as a Warp Cannon, though unlike in New Super Mario Bros., it launches the player to World 6 instead of World 7.

World 4 also appears in Mario & Sonic at the London 2012 Olympic Games under the name "Cheep Cheep River" as the location of the Dream Rafting event. Porcupuffers, Thwomps, Cheep Cheeps, and Bob-ombs appear in it, as well as the addition of Gooper Blooper. Also, Wendy (the boss of this world) appears as a costume for the player's Mii.

New enemies

 * Big Urchins
 * Porcupuffers
 * Huckit Crabs
 * Bloopers
 * Blooper Babies
 * Blooper Nannies
 * Cheep-Chomps
 * Scaredy Rats
 * Climbing Koopas
 * Fishbones
 * Skewers
 * Mechakoopas
 * Burners
 * Wendy O. Koopa (Boss)
 * Bowser Jr. (Boss)

Trivia

 * The background music for this world was remixed in Puzzle & Dragons: Super Mario Bros. Edition as the music for World 4.