Enter the green pipe at Point 1 to find a room with a Roulette Block.
The first Star Coin is located at Point 2. Swim through the gaps between the Caterpillar Blocks and grab it.
Toss fireballs into the ! Pipe at Point 3 to reveal a stash of coins and an Super Star.
If you have a Gold Flower power-up, use it to destroy the Blocks at Point 4. Enter the exposed pipe to find a room filled with Blocks, then use your gold fireballs to turn them all into coins!
The second Star Coin is located in a hidden room. To find it, enter the yellow pipe at Point 5.
There’s a Spiny Cheep Cheep swimming near the Star Coin. If you managed to hang on to a Fire Flower power-up, use a fireball to clear out this pesky enemy before you collect the Star Coin.
The third Star Coin is floating at Point 6. Make sure you grab it as you weave through the Urchins and Caterpillar Blocks.