World 1-A (New Super Mario Bros.)

World 1-A is the only optional level in World 1 of New Super Mario Bros..

Layout
First, the player has to go down the Warp Pipe, and they will end up in an underwater world. A ? Block containing a power up can be found at the beginning. At this point the screen will scroll automatically, and Mario will be crushed if he gets stuck between the screen and a solid object. Sushi will appear at both the top and bottom of the screen, two each time. Sushi can be defeated quickly by Fire Mario's fireballs.

The player can find a P Switch while swimming along this level. If the player hits it, it will produce Silver Coins between bouncy obstacles. Then, by going high as possible, the player can grab the first Star Coin. From there, Mario can go right to enter a pipe leading upwards, which will take him to the area with the second Star Coin.

When Mario enters the underwater world again, he should hit the Roulette Block while avoiding the Cheep Cheeps. The player has to dodge the Sushi coming from the left, and then they can go through a Red Ring to collect the Red Coins. The Sushi will now switch back to attacking from the right, and Mario should avoid Pipes that spew bubbles. Another P Switch can be found, allowing Mario to collect more Silver Coins.

The player has to swim right as soon as the third Star Coin appears above. Mario then has to swim past the last few Sushi and head up the pipe, which will lead to the Goal Pole.

Star Coins

 * Star Coin 1 - On the top of the level, the first Star Coin can be found guarded by Hidden Blocks, so Mario should collect the coin from the side.
 * Star Coin 2 - Right after the first Star Coin is a pipe. Mario should take it, and he will be transported above ground where the second Star Coin can be found.
 * Star Coin 3 - Mario will have to maneuver himself around a stone structure to the right opening to obtain the final Star Coin.

Enemies

 * Cheep Cheep
 * Sushi