Take the first yellow pipe in the stage. Ground pound the POW blocks to descend the room and collect the Star Coin.
Take the second yellow pipe after the checkpoint (just before the red ring). Use the Gold Flower to make a path to the Star Coin, without removing too many Brick Blocks.
Before the pipe stairs there is a section with two block platform towers, a Red Koopa Troopa and a few Koopa Paratroopas. Bounce off a Koopa Paratroopa to get on the level of the Koopa Troopa, then bounce off that to get to the highest level. The Star Coin is above the right tower. If you have a Super Leaf, you can also fly up to make things easier.
After the first Deep-Cheep, there is an alcove with the first Star Coin. Quickly swim to the right to get into the alcove before a moving wall blocks it off. A second wall will move to open the way out of the alcove – this might be a chance to grab the Star Coin if you were blocked off earlier, but beware getting crushed.
After the red ring, you will come to a section with Urchins and notches. The Star Coin is easily seen and collected – just wait for the Urchin guarding it to descend.
After the second Star Coin, a few walls will move, opening to an area with a green pipe guarded by an Urchin. Swim up to and enter the pipe when safe (a Fire Flower may help), and when in the next room swim all the way to the top to claim the last Star Coin before it gets blocked off by the closing walls.
Take the left door. Hit the switch on the right in the next room, and climb up the appearing platforms for the Star Coin (watch for the Boo). Exit by using the left switch and its appearing platforms.
Take the middle door in the group of three that you come to next. This room has hidden floors that you can bounce on. Use them to reach the top, hit the switch, and make the Star Coin appear at the lower left of the room.
There is a room with three switches and three paths to the right. Hit the middle and right switches and take the top path. You will see two openings above: enter the one on the right by wall-kicking or flying, hit the switch (the Star Coin will appear), drop down and fly/wall-kick up the left opening to snag the last Star Coin.
This Star Coin is easy to spot. Use the unstable platforms to grab the Star Coin, land on the smaller unstable platform, and jump back to safety. Raccoon Mario makes this easier with the scuttle.
After the checkpoint room, you’ll see the Star coin above an unstable platform. Use the lift platforms to snag the Star Coin before it scrolls off-screen.
After Star Coin 2, you’ll see a section with Buzzy Beetles and a POW Block with a brick block in front of it. Use the lower Buzzy Beetle’s shell to hit the POW block (or use Raccoon Mario’s tail), then hit the second POW block trapping the Star Coin. Grab it by wall-kicking or using the lifts.
When you see the Star Coin, just ground pound the blocks to get it.
When you see the Super Whomp, DON’T go down the green pipe. Instead lure the Super Whomp into toppling over, then continue right to find the Star Coin amongst a ring of coins.
Don’t enter the door to the boss. If you don’t have the Super Leaf, grab one by hitting the hidden block between the blocks to the right of the boss door. Build up enough speed to fly around the left side of the wall (don’t fly straight up as the flippers block you). The last Star Coin is yours.
You’ll need to use your momentum on ice and perform a ducking slide to get this Star Coin. Beware of the spiked ball.
Take the right path just after the coin outlines and you’ll get this Star Coin with no hassle.
You’ll see two spiked balls at the level of the third Star Coin. You can take your chances and grab the Star Coin during an opportune moment where the balls are moving away (watch out for the Dry Bones), or use the large spiked ball (hit the switch to release it) to ‘defeat’ the smaller balls and make the attempt easier.
The Star Coin is to the left, just above the ends of the first paired vines you sprout (right after the group of four at the beginning of the scrolling section).
Hit the POW block above the Chain Chomp and stay on the right vines. As soon as you see the Star Coin, make a shallow jump and grab it – if you leave it too late, or make a great leap, you’ll land on the platform above and can’t get back down again.
At the gold ring, use the two Koopa Troopas’ shells to sprout four vines. The Star Coin is between the middle two vines, surrounded by a group of five circling Koopa Paratroopas.