Level Up 1
Jump into the canal in the center of town and swim out to the ocean. Turn right when you hit the ocean and then right again. There's a level up mushroom down in a nook there.

Level Up 2
Go to the beach by the 2 beach umbrellas. The sunglasses guy is in one of them. Face the umbrellas with your back to the water. Now move just right of the rightmost umbrella. Jump around here a bit - you should see a circle outline appear on the ground. Slam that for a secret sewer entrance with 8 coins and a level up mushroom.

Level Up 3
hey i just wanted to let u know i found a level up mushroom in the central delfino plaza that u didn't mention on ur page. well on the beach where the guy selling sunglasses is and the 2 umbrellas... ok swim out to that little island. the guy out there has a small campfire smoldering. if u squirt the fire, a mushroom pops out. but u have to be quick to catch it, it runs around.
Ranae :)

Level Up 4
Go in the sewers at marketplace. Go right right right and left.

Coin Hints
Spray every wanted poster. Spray every sign. Spray every open window.

You can get infinite coins by having throw-guy throw you - the coins will reset but your coin count won't reset.

Super Mario Sunshine Walkthrough