Eely-Mouth is a supporting antagonist living in Noki Bay in Super Mario Sunshine. It is a giant eel with two eyes on each separate side which polluted the water. It appears in the fourth episode of Noki Bay, Eely-Mouth's Dentist.
The Noki Elder explained to Mario that the culprit of Noki Bay was Eely-Mouth, who caused the bay to be polluted with its gingivitis. The Noki Elder will give Mario a diving helmet in order for him to stop Eely. Mario was able to defeat Eely by spraying its purple teeth to make him stop polluting the water.
Eely-Mouth is a very dangerous boss. First, Eely will spread toxic bubbles which can damage Mario. They can be sprayed, but they give Mario air and the small bubbles don't harm him. Mario must spray water with F.L.U.D.D. at its teeth to clean it. Eely will also attempt to suck Mario in its mouth. If Mario is sucked inside, he will lose air. Eely will also spin very fast and then open its mouth. After Mario has brushed all of its poisonous teeth, the eel will give up its golden tooth. This will grant a Shine Sprite and twenty Coins in a shape of a heart (possibly thanking Mario for cleaning its teeth).