You will need your Gamecube and your Super Mario Sunshine game.
Go to the Delfino Plaza and find the red box. Proceed to stomp on it.
Go to the entrance of Corona Mountain. Enter the cave.
Once you are in the cave, you will see this. Use the hover nozzle to float over the spikes and fire.
Once you arrive at the other side, pick up the green mushroom.
Use the hover nozzle to fly over the next set of spikes and fire.
Once you arrive at the other side, there will be a sprinkler. Run into it to restore your water.
Hop on the boat.
Switch to the regular nozzle and spit the water to the back of the boat. By doing this, you will propel forward.
At the end of the river, stomp on the red box.
Use the rocket nozzle to climb the clouds. Once you are at the top, you will see a dark cloud. Ascend into it.
You have made it to the boss!
Watch out for Bowser's flames and Bowser Jr.'s Bullet Bills!
Use the rocket nozzle to ground pound one of these red things. There are 5 total.
Once you ground pound it, run to the bowl.
Once Mario falls from the sky, his pump dies :(
You have restored peace to Isle Delfino!
The creator of this guide has not included tools