World 8-3 (New Super Mario Bros.)

World 8-3 is the fourth level of World 8 in New Super Mario Bros.. It becomes accessible after completing

Layout
This level is another underwater level, and contains the second and last appearance of Unagi and Mega Unagi in the game.

The player starts outside the main level, with a pipe taking them inside. In the very first section are two Bumpers surrounding a ? Block containing a Fire Flower. As the player swims upwards, they encounter various Unagi; some stay in place and lash out when the player gets near, and some travel horizontally. After passing through a group of Unagi and a Red Ring, the level's midway point is reached rather early on.

After the midway point, a Mega Unagi is seen on the left side of the screen, and as soon as the player becomes level with it, it will chase after them. The Mega Unagi will chase the player through the rest of the level, and will destroy all Brick Blocks in its path; the player must swim quickly to avoid it, while also dodging regular Unagi, Cheep-Cheeps, and Bumpers along the way. The player can use pipes with rushing water to boost their speed and get farther away from the Mega Unagi.

If the player stops swimming, the Mega Unagi will stall with them. After a certain amount of time passes, the Mega Unagi will try to crouch down on the player, and then swim away offscreen. The Mega Unagi will not respawn as long as the player doesn't stall again (otherwise, the Mega Unagi will respawn after a minute), meaning the rest of the level will become much easier if the player survives.

At the end of the Mega Unagi chase section are two pipes; a green pipe on the lower end, and a red pipe above it. Both of these pipes will take the player to the flagpole, though the red pipe will allow the player to reach the top of it by stomping on a single Koopa Paratroopa.

Star Coins

 * Star Coin 1: Slightly over halfway through the level; found on the floor.
 * Star Coin 2: Almost immediately after the first Star Coin; found on the ceiling behind Brick Blocks.
 * Star Coin 3: Towards the end of the underwater section; found above a pipe on the floor.

Trivia

 * This is the only underwater level that does not have its usual music, being replaced by the underground level's music to fit the darker theme of World 8.