You’ll start encountering some new enemies in this stage, such as the Galoombas and Skipsqueaks. The former are like Goombas, but they take two hits to defeat, while the Skipsqueaks will simply jump in place. Start off by snatching the coins around the area, then use the clear pipe at the back end to reach a cliff. If you have the Cat Suit, simply climb this wall to Green Star #1 but if you don’t, hop down to a ?-Block with a power-up (which happens to be the Super Bell, if you’re big) first. On a tiny island in the water south of there is a P-Switch that has a “M” on it.
This requires you to have a specific character, in this case you need Mario, to step on it. Stepping on the switch as Mario will give you the level’s Stamp, but you can always replay it with that character, should you not be using him right now. Head through the pipe leading right and go under the far hill for a 1-Up Mushroom. There will be a Red Ring here, so go through it and collect all eight coins to get a Super Bell. If you climb the tall left and right ledges you can get some coins to appear, but otherwise continue to the far north, navigate the platforms and go down the pipe.
Once underground, you’ll want to take the top path to find a power-up from one of the ?-Blocks. At the end of the floor, jump up and climb the wall to a bunch of coins (if you have the Cat Suit), then drop down to the green pipe. This will lead you to a room with a bunch of tiles on the floor, which light up upon stepping on them. Simply step on all of the tiles, including the “stairs”, which will net you Green Star #2. Head back out and don’t be fearful of falling by the rotating wheels, instead willingly doing so to find a bunch of coin blocks and Green Star #3. Use the pipe to head back to the top, then enter the next pipe to reach the final area. There will be a Super Mushroom in one of the wooden boxes to the right, if you need a power-up. Use the rolling hills to reach the top of the Goal Pole.