If you have a Gold Flower, use it to destroy the Blocks at Point 1. When the path is clear, enter the purple pipe to find a room filled with Blocks.
The first Star Coin is located at Point 2. Continue to the right until a boulder appears, then lead it back to the Star Coin. After the boulder destroys the enclosure, you’re free to collect your prize.
The second Star Coin is located in a hidden area. Enter the yellow pipe at Point 3 to find it.
When you approach the Star Coin, it moves to the room’s right wall. As you follow it, stay near the bottom of the area to avoid the Bloopers as they spring out of their pipes.
If you’ve managed to hang on to a power-up, consider clearing the Bloopers out of the area before you pass through the Red Ring at Point 4. After you pass through the Red Ring, the red coins appear in two spinning clusters to the right.
When you trigger the P Switch at Point 5, a trail of blue coins leads you into a nearby pipe. You can only enter the pipe while the P Switch is active, so move quickly!
The third Star Coin is located inside another enclosure. Swim near Point 6 until a large boulder tumbles toward you. When it does, take cover in the space below the pipe to the right. After the boulder destroys the enclosure, swim over and grab the Star Coin.