The Secret of the Dirty Lake

"You know the Cliff Spring Cave on the far end of the lake? Some nasty ooze came spilling out of it with no warning at all! Now, our beautiful lake is contaminated. It's so yucky!"

- Pianta

The Secret of the Dirty Lake is the sixth episode of Bianco Hills in Super Mario Sunshine. The episode's objective is to collect the Shine Sprite at the end of the secret obstacle course.

Layout
The entrance to the secret area is through a cave at the back of the large lake. However, the cave was barred off to prevent the Graffiti inside from pouring out. Shadow Mario broke the barrier when he ran inside, which ended up polluting the entire lake. In order to get to the cave, Mario has to make use of several lily pads to traverse the lake, as trying to swim in the lake will deal damage to Mario. The lily pads will start to disintegrate as soon as Mario stands on one, so the player has to quickly move from one pad to the next in order to avoid falling in the water and make it to the cave. Just before the cave, there are a few logs the player can use to to climb to the entrance, which has a box with the Turbo Nozzle in it. Collecting this nozzle will unlock it for this level.

Upon entering the cave, Shadow Mario will appear to take F.L.U.D.D. away. Mario will then be brought to an area with a series of moving platforms. The red and blue ones flip alternatively and the white cubes move and turn as Mario is on them. Mario will first have to jump between a set of red and blue platforms as they flip to reach the large blue platform afterward. Next is a large cube that will start spinning as it moves along once Mario jumps onto it, though the gap between it and the blue platform Mario is already on is wide, so the player needs to use either a Wall Jump or a Spin Jump to reach the cube. Should the player fall on the platform below, they can use a trampoline to jump back up. The large cube will bring the player to a long yellow platform with two arrow-shaped blocks that slide across it, pushing Mario off the edge if the player isn't careful. Next is another cube platform, but this one scales vertically and rotates as it moves upward. The player needs to stay on the block as it climbs to reach the next yellow platform. Afterward is the final set of red and blue flipping platforms the player needs to cross, though these ones are more spread out that the earlier set. On the final green platform is the Shine Sprite.