Downtown: Helping Sandy Clean Up Trash:

To get this letter tile, you must wear your Reef Blower costume. Sandy then appears somewhere on Shell Street in the Business District. Then, simply blow the trash into the sewer holes.

Before you find the last tile in Downtown, you must complete Sandy's Treedome, Jellyfish fields, Goo Lagoon, and get all the other letter tiles in Downtown Bikini Bottom. Go to Downtown and do not go anywhere else. Keep looking for Sandy until you find her. After talking to her, big balls of trash will appear. Dump them in the sewers and claim your letter tile. To roll them in the sewers, you can also use you Reef Blower.