OK, you have a little practice with the game now. It's time to face a real boss. Your enemy, the Big Plant, is up on the windmill.

Go over the new ramp created in Episode 1 and then cross the bridge. Stay on the hedge as you go up the path. There'll be a water spigot at the end - stand in its stream to fill up your water. If you run into any thorns blocking your path, use the hover-nozzle to go out and around them. Note there's a M to wash past the guy there.

Jump on the arm of the windmill as it goes past, and then up on the roof to the boss. You both will fall into the center. Note that you want to conserve your water in here, don't go wild! Follow him around until he opens his mouth to spit goo out. When he does, send a CONTINUOUS stream of water into his mouth to bloat his belly. When he's full, he'll fall over and his belly button will poke out. Jump on him and then do a jump-pound to squash him. You'll have to do this 3 times to kill him and get your shine!

Super Mario Sunshine Walkthrough