Super Mario Bros. 3/World 3 Part 3

Part 1

 * This is a level where the Frog Suit is very helpful. Enter the pipe in the water to proceed to part 2.

Part 2

 * Since the Roto-Disc spins clockwise, you might want to swim above, rather than below it.
 * Two Cheep-Cheep are guarding a block containing a Fire Flower here. Grab it if you want it, then continue.
 * The pipe at the end leads to part 3.

Part 3

 * Here, you'll encounter a new enemy: Stretches. These are essentially Boo Diddleys stuck to a white block. They can still do damage to you if you aren't careful.
 * Avoid the first group by swimming barely above the pit. For the second one, swim up to the ceiling. After that, you have to swim between the two last Stretches, which is very hard without the Frog Suit.
 * The pipe at the end leads to part 4.

Part 4

 * Run forward to meet Boom-Boom again. This time, there are two blocks in his room, which can either help or hinder you. Stomp on him three times or feed him five fireballs to defeat him.

3-8

 * This level has Boss Bass again to eat you. The blocks move farther than they did in 3-3, so watch out.
 * Jump on the first pillar, then wait until the blocks move down. When they move up again, go forward and kick the Koopa shell against the left block to reveal a vine. Climb it up to safety and jump on the note block to reveal a fire flower.
 * When the blocks move up again, continue to jump until you're on a platform with ice blocks. Kick them away, then jump at the brick block for some coins.
 * There's a single brick block with a 1-up mushroom. You need to be Raccoon Mario to get it.
 * Kick the next Koopa Troopa against the right brick block to reveal another vine where you can hide from Boss Bass. Two platforms further, there's yet another vine in a brick block.
 * Before the end, the path splits into two. The shorter and by far easier way is the top one, which leads straight to the pipe. The bottom one leads to several coins and a P-Switch which turns the brick blocks here into coins. You can then get a 1-up mushroom from the topmost "coin".
 * Collecting 44 coins in this level unlocks the White Mushroom House. This requires taking the bottom route to get the coins there and using the P-Switch.

3-9

 * This area is filled with bullet bill cannons, as well as a new enemy: Bob-ombs. Jump on them, then kick them somewhere and they will explode, taking out nearby enemies.
 * After the Piranha Plant, jump at the sixth brick block from the left for a raccoon leaf.
 * For a shortcut into the water, stomp the first Para-Troopa, then quickly carry the shell to the right and kick it against the wall of brick blocks. Run through and jump onto the pipe, then go down into the water. You need to be quick to make it before the Koopa Troopa resurrects, and the bullet bills are sure to make it hard.
 * When you see a group of note blocks, jump on the middle one for a Fire Flower. Kick away the ice blocks to reach it.
 * When you see a Koopa Troopa trapped in ice blocks, the single brick block contains a 1-up mushroom.
 * In the water, swim all the way to the left and take the pipe to end up in a bonus area (see below). Otherwise, take the rightmost pipe to be taken to the ending area.
 * In Super Mario All-Stars, the layout of this area was slightly changed to fix a glitch.

Bonus area

 * Hold to the right to get to a giant ? block, jump at it to get a Frog Suit. Afterwards, exit the area, you'll return in the middle of the water area.

Airship

 * After the cutscene where Mario discovers that the King has been transformed into a Spike, Mario jumps on the airship to fight the boss of this world.
 * At the beginning, try to avoid the Rocky Wrenches. It is a bad idea to stomp on them because they tend to push you right into a bullet bill.
 * Behind the bullet bill shooter, wait until the passageway is fully on-screen then quickly run through it to avoid the cannonballs. At the top, there's a block with a raccoon leaf.
 * After another such passageway, you'll see another new enemy: rocket engines. These spit flames which hurt you, so avoid them at all costs. They reside at the bottom, and you must jump on the nut at the top to move forward. The screen will catch up to you, so at the end, make a quick jump to the other side.
 * When you see the Rocky Wrenches near the end, watch out for the rocket engine in front of you. Jump when the flame is out.
 * The pipe takes you to Wendy O. Koopa. She throws a ring at the beginning which moves around the battlefield and must be avoided. For each time you stomp on her, she will release another ring. You can also shoot her with ten fireballs to kill her. Afterwards, take the wand to get to the next world. Princess Toadstool gives you a Music Box for beating this world.