The Hillside Cave Secret

"Say... Do you know anything about the Hillside Cave? I was hanging out near the entrance the other day... Suddenly, this weird-looking guy ran after me! I took off quick! I saw him bust the cave gate open and vanish inside. Yikes!"

- Pianta

The Hillside Cave Secret, also referred to as The Hillside Cave Mystery,  is the third episode of Bianco Hills in Super Mario Sunshine. The episode's objective is to collect the Shine Sprite at the end of the secret area. After completing the episode once, the player can either return to this episode or enter the Hillside Cave from Episode 4 on to collect the Secret Shine Red Coins of the Hillside Cave.

Layout
Starting in this episode, Seedy Pods and Pokeys appear in various areas of the level, with many of them appearing near the lake.

In order to get to the cave, the player needs to enter the lake area once again. Before going through the large gate, the player can find a Pianta covered in goop. After cleaning him off with FLUDD, he will tell Mario that a mysterious person broke through the wall blocking the cave. After passing through the gate, the player has to take the ropes connecting the platforms, which start under the bridge leading to the Big Windmill. To get to the last platform, the player has to use the Hover Nozzle, then simply jump onto the ledges leading to the cave entrance above.

Upon entering the cave, Shadow Mario will appear and take FLUDD away from Mario, then Mario will be brought to an area filled with moving platforms. The first set of platforms move side-to-side and are needed to reach the higher stationary platform. Next is a series of moving and stationary platforms, with the moving ones each moving in a different way. After traversing these platforms is a long bridge with four large, spinning cubes that slide across the bridge. Taking care not to be pushed off, the player has to cross the bridge to the next group of platforms, which are spinning star-shaped ones. Jumping between these and making it to the end will reward the player with the Shine Sprite. If the player decides to collect 100 Coins in the Hillside Cave (by collecting close to 100 of them and collecting the 100th coin in the secret area), the 100 Coin Shine Sprite will appear on the platform just before the two spinning star platforms at the end of the level.

If in this episode Mario talks to the tourist Pianta at the base of the Big Windmill who gives him the Blue Coin after cleaning him, he tells him, "I came here to tour the Big Windmill...and I've got to say, it's spectacular!"