World 3-Tower

From the start, hit the blocks to get a Fire Flower.

If the Fish Bones spots you, it will charge toward you, but it defeats itself upon hitting a wall. Beat this one, then swim to the left behind it.

Swim through the narrow passage below the seemingly solid wall, and you will find a hidden room. Avoid the Fish Bones and jump out to get some coins and Star Coin #1 above.

Swim back through the passage to the right and take the pipe to reach the next room.

In this room, you will be swimming upward as the large blocks move back and forth. Collect a bunch of coins at each level, as well as Star Coin #2 on the right side.

Following the two center blocks as they move upward, you will now need to watch out for spiky columns above.

SECRET EXIT: If you have a Mini Mushroom, follow the right square block as it moves to the right (below the spiky columns). Enter the mini-sized pipe and continue swimming upward through the trap-filled rooms until you reach the surface. Then, exit via the pipe and hit the blocks to get regular Mushrooms again, and head right to the secret flagpole. This secret exit opens the path to the Green Toad House and the Cannon, which will lead to World Flower.

When the spiky columns above retract, swim upward through the center to reach the Checkpoint (a save point).

Continue swimming upward and you will come to an enclosure with a red ring and water currents pushing you back and forth. Collect the red coins to get a free Fire Flower, then swim into the upper-left green pipe to reach a hidden room. Collect Star Coin #3 in here, then go down and right to exit.

Just like you have been, keep moving upward while evading the Fish Bones.

When you reach the spiky columns again, swim still between the two solid walls in the center since that is a safe spot.

Just above that, go through the pipe to reach a dry room. Hit the blocks to get a Fire Flower, then head through the double doors to meet the four Reznors. Defeat them as usual and the tower will be cleared.