Tiny Pothole

Tiny Pothole is the very first cave Olimar enters in Pikmin: Lair Of The Umbrax Dweevil.

Rock Pikmin are first found here, by throwing pikmin into the Slate Candypop Buds that are growing on the second floor.

It is located in Forest of Dreams.

First Floor
Enemies: NONE | Pollutistopper parts: Twisty Lock | Pikmin found: NONE

Just pick up the Pollutistopper part here and go to the next floor.

Second Floor/FINAL FLOOR
Enemies: NONE Pollutistopper parts: Drainage Blocker (stuck in crystal) Pikmin found: 8x Rock Pikmin (from candypop buds)

The part you need here is stuck in a crystal, so bring some Red Pikmin up to the Slate Candypop Buds and rediscover the Rock Pikmin, which you can use to get the Pollutistopper part out of the crystal.