NOTE: As their name suggests hints are not exactly Super Mario Sunshine cheats, and are usually just simple (but very useful) tips on how you can unlock secret level, features, find hidden areas and such. Hopefully these will make playing Super Mario Sunshine even more entertaining.
Open tube
Have you seen the island that the guy was shipwrecked onto? If you do, then you should have seen the hot blob on the green tube. To get it out, you need the Yoshi that is on the rooftop of Delfino Plaza. Put Yoshi onto the three boats. Once you get to the island, use Yoshi's juice to spray the blob. It will disappear and you will be able to enter the tube.
Get Yoshi fruit from Trees
There is another way to get Yoshi fruit from trees. First, turn the grey control stick around as fast as you can. Then, press the "A" button. Finally, press the "R" button. Yoshi will spin in the air and spray all of the fruit off the tree.
How Yoshi can take care of himself
Are there times when you want to leave Yoshi somewhere safe while you go somewhere else. Well, now you can. In Delfino PLaza, take Yoshi to a fruit stand or somewhere with fruit. Leave him there and he will eat fruit by himself. If you go through one of those colored portals and come back to Delfino Plaza, Yoshi will be back in his egg.
During the flood, go to noki bay entrence (DO NOT GO IN) Turn towards the fountain, you will see the stuff that is above the fruit stand. Go on the shorter one and face the taller one. Then fall thru the middle and imidiatly use the hover nozle and hover UNDERWATER. It will stop and you can breath underwater!
Return to the Airport
Once you've beaten the game (and saved your game), you will be able to go back to the Airport from the very beginning. It'll cost you, though. For the price of 10 coins, a boat close to the clocktower where you find Yoshi will take you to the Airport level -- which is filled with coins and fun stuff to do. Give it a try!
Sunglasses and Hawaiian Shirt
Want to see Mario in a different outfit than his trademark blue overalls and red shirt? How about putting on some shades and slipping into a shirt that would make even Tom Selleck jealous? The shades are easy to get. Look for a man with black sunglasses in the hub world (he's at the beach, close to the fruit stands) or in most of the other levels and talk to him. When you've gotten 30 Shines, he'll give you a pair of sunglasses to wear, which will darken your screen appropriately. Note, the sunglasses will disappear the moment you step into another level or restart the game.
The same guy will also give you a Hawaiian shirt -- but you've got to do some work first: finish the game. If you've saved your game after you beat the last big boss, you'll be able to get your shirt anytime you talk to this guy.
Bubba-Proof
In Gelato Beach and other levels where there are Bubbas (the big red fish that drags Mario underwater), you can keep them from doing this attack with this little trick.
Pick up a piece of fruit and start swimming with it. It will enable a glitch where they cannot drag you. This is very useful for the Red Coin Shine in Gelato Beach.
Conserve Lives
To build up Mario's stock, try to quit stages when you are about to die. This would apply to stages like the racing stages (with the Islander who likes to race) and some of the mini-stages (like the Pachinko stage).
If you can restart the stage easily (and quickly), you should learn to quit when Mario is in danger of dying. This will let you have a large stock of lives to tackle stages and mini-stages that you want a lot of lives to spend on (the Dead Leaf in a Dirty Brook mini-stage comes immediately to mind).
Fast Lives
Go to Pianta Village and Choose the episode titled "Piantas in Need" and save all the Piantas and the villagers who gave you blue coins before will now give you 1-ups instead.
You can quickly gain lives once you finish the game: start by collecting 10 coins then going to the Airport; collect 50 gold coins at the Airport; now select quit without saving to return to town; head back to the Airport and collect 10 coins to reach the magic 50 mark again. Repeat ad nauseum.
After obtaining the Rocket Nozzle in Delfino Plaza, blast to the roof of the building directly behind the fountain where your nozzle boxes are located. Go down the pipe to enter Sirena Beach. Be sure that you select episode-1 (The Manta Storm). Head immediately toward your left and ground-pound the middle crate. An extra life will appear. Then go to the right-side of the board where the electrical slime is. Clear the slime between the hut and the tree to rescue two friendly characters. Talk to them and they'll each give you an extra life. Exit the area and repeat as often as you like. This takes less than a minute.
Music Fudging
This trick works on the Gelato Beach level in the stage, "Wiggler Ahoy! Full Steam Ahead!". Battle Wiggler as usual, then, when you've ground pounded the worm the third time, you'll hear the boss music slow down. Before the Shine Sprite appears, press Z to view your map.
If you timed the Z press correctly, you'll hear the slower remix of the boss music! In the map mode, hit cancel, then IMMEDIATELY press the Z button again to listen to a much faster remix! This doesn't give you any extra lives or anything, BUT it is useful if you love game music!
Running Nozzle Trick
When you get the running nozzle, (The one that dark Mario steals) then you can do a trick where you use it but do not run your water down. What you do is that you hold R to charge up. Once charged, you will run, but once you run, jump and let go of R. Then before you land, you quickly hold R again, but hold it about half way down. You will still be running, but you won't lose any water. Try it and see for yourself.
Yoshi spin jump
You can use Yoshi to jump much higher than the normal yoshi hover jump by rotating the analogue and pressing A, the spin jump can be executed as with Mario as well but you have the added bonus of being able to hover by holding A at the peak of the jump.
Secret Moves
There are a couple of undocumented moves in Super Mario Sunshine that come in handy:
Sprinkler Backflip: While spraying water forward (standard nozzle), press the A button to perform this backflip that sprays water at the same time.
Water Slide: Create a small puddle of water in front of yourself, then perform a head dive. You will now slide forward on your belly, slowly picking up speed until you cancel the slide by pressing A.
Yoshi Sprinkler: You already know that you can get rid of large areas of paint quickly by rotating the Analog Stick quickly, then pressing R to send Mario's water whizz everywhere. You can also do this while riding Yoshi.