This level has a bunch of Peepas, Boos, and Big Boos, so snag a Light Box right from the start, as you will be needing it. Jump on the raft and pass under some chain-link fences, or climb up them if you have the Cat Power-Up. If you don’t, then leap off at the platform, jump on top of the long ?-Block and wall jump up to the top of the cage. When on top of the cage, you will back to backtrack a tiny bit to get Green Star #1. Get back on the raft and ride it to the first piece of actual land. Some normal Boos and a Big Boo will appear, so destroy them with the light, then get ready to get on the raft on the other end.
As soon as you do, there are some invisible cloud platforms off to the side, which leads to Green Star #2. Get back on the raft, then ride it to the end of the course. Defeat the three Big Boos to make a Warp Box appear, but avoid trying to go in it right away. If you have the Cat Suit, you can climb the wall to grab Green Star #3. If you don’t have the Cat Suit, try to jump on top of the Light Boxes to get the star. Get in the Warp Box now to enter the Goal Pole area. There will be some invisible cloud platforms here that allow you to reach the top of the flagpole.