Eely Mouth is an eel-like boss that serves as a Boss in Super Mario Sunshine where it is fought in the Noki Bay. Its gingivitis is the cause of the widespread pollution in the area and Mario has to clean its mouth with F.L.U.D.D. to heal the suffering creature, which is considered a boss battle by the game.
In order to beat this boss you must shoot his eight teeth with F.L.U.D.D. to clean them and obtain the Shine Sprite tied to the episode, which is in fact hidden in its rotten golden teeth. Eely-Mouth main method of attack is its periodical sucking of the water around it, which can result in Mario being sucked inside its mouth and damaged. Eely-Mouth will also release toxic bubbles from its mouth, which can damage Mario as they are assumed to be the direct source of the pollution. After its eight teeths are cleaned, Eely-Mouth will recede into its cave leaving its rooten golden teeth behind and thus the Shine Sprite.