Dune Bud Sand Castle Secret

"Have you ever heard of the Sand Portal? It's a sand castle that appears, then crumbles away quickly. I guess it must not have a very good foundation..."

- Pianta

Dune Bud Sand Castle Secret, also referred to as Dune Bud Sand Castle Secrets or Dune Buds and Sand Castles,  is the first episode of Gelato Beach in Super Mario Sunshine. The episode's objective is to collect the Shine Sprite at the end of a secret course. After completing the episode once, the player can return to this episode to collect the Secret Shine Red Coins in the Sand Castle

Layout
In order to enter the secret course, the player must first reveal it. By spraying a Dune Bud directly in front of the beach's peninsula, a large sand castle gate known as the Sand Portal will appear out of the sand, with a rotating red arrow guiding the player to the arched doorway as the sand castle gradually crumbles away. The player needs to run or dive into the gate before it crumbles completely, in which case the player has to spray the Dune Bud again. Though the doorway appears to lead straight through the Sand Portal to the other side of the castle, when Mario enters it, he will be instantly transported to a secret level (though he can enter the Sand Portal from the other side of the doorway as well). Upon entering the secret level, Shadow Mario will take FLUDD away as usual.

The player will start on a square platform facing a path of sand blocks. The player needs to cross the sand blocks to reach the next platform, but the sand blocks will start to fall once Mario stands on them, so the player has to move quickly. Beyond the next platform is a longer path of sand blocks, though the path also bends slightly. Crossing this path will take the player to a large sand castle made out of sand and Hard Blocks. At the top of the sand castle is the Shine Sprite.

Trivia

 * While the Sand Portal is created via a Dune Bud, it is different from the other sandy structures that are created by Dune Buds because it gradually sinks back down into the sand once raised, as opposed to sinking back down immediately, and also because it appears far away from the Dune Bud that creates it, as opposed to appearing directly under it.