World 3-A (New Super Mario Bros.)

World 3-A is the first secret level of World 3 in New Super Mario Bros. The level is a coastal level, featuring Skeeters. This level is unlocked by paying five Star Coins at a Star Coin Sign at the beginning of World 3, allowing the player to play this level in favor of World 3-1.

Layout
This level starts with Mario jumping onto several floating barrels, while avoiding Skeeters. After passing the Red Ring, there are several moving platforms. Mario needs to jump on the last one while avoiding the Skeeter to get onto the next platform. After that, Mario should hit the ! Switch to activate the red blocks for him to continue. To get the first Star Coin, Mario needs to either let the Skeeter use a bomb to destroy the blocks that block the Star Coin, or he can go into the water, and swim low enough so that the player can go under the blocks, but not low enough to lose a life. To get the second Star Coin nearby, Mario needs to jump off the Koopa Troopa below the coin. After going through the Warp Pipe, Mario can get the third Star Coin by going into the next Warp Pipe and, as Mini Mario, he should run on the water and jump to the Star Coin. After this, Mario should go past the moving platforms to the final Warp Pipe, reaching the Goal Pole.

Star Coins

 * Star Coin 1 - After the checkpoint, Mario can find a lone Skeeter. The Star Coin is protected by brown blocks and requires the Skeeter's bombs to penetrate it, or the player can just swim directly under the blocks and then up to the coin.
 * Star Coin 2 - After the first Star Coin, the second Star Coin is in midair and requires Mario to jump off a Koopa Troopa or Skeeter to get it. He can also collect it by jumping off of the barrels if he times his jumps correctly.
 * Star Coin 3 - After taking the Warp Pipe to the second area, the player should become Mini Mario and take the regular Warp Pipe, not the small one. They should run across the water and jump to get the final Star Coin. The coin can also be obtained by using a Mega Mushroom.

Enemies

 * Skeeters
 * Koopa Troopas
 * Koopa Paratroopas
 * Mini Goombas
 * Cheep-Cheeps