Here's the official post:
"The storyline in Super Mario Sunshine is much different than what you might expect. This time, things are much more complicated than simply rescuing Princess Peach from Bowser. The adventure starts when Mario and Peach decide to take a well-deserved vacation to a beautiful island in a remote location. Since the island is perpetually sunny and inhabited by friendly locals, it seemed like the perfect choice at first.

In typical fashion, poor Mario never gets a chance to relax. When he arrives on the island, he notices ugly scribble marks covering the walls throughout the community. What's worse, the person responsible for the scribbling has disguised himself to look just like Mario!

Mario is falsely accused by the locals, so he decides to get to the bottom of things. Armed with a new water-pumping backpack, Mario sets out to clean up the scribbling and reveal the identity of the true villain."

Interesting, no?