Gringills are orange-brownish eels with large teeth and large eyeballs. Their pupil nearly covers their eyes. There are two variants: large Gringills that stay in their caves and small Gringills that are small and move around.
Gringills are not too dangerous as long as Mario keeps his distance. This is because when they chomp with their teeth, it creates an electric spark that spreads out through part of the water. Their main weakness is the Koopa Shell, which can destroy them in one hit. Gringills are impossible to destroy in Super Mario Galaxy 2 without a Shell.
Gringills appear in Beach Bowl Galaxy, Sea Slide Galaxy, Bigmouth Galaxy, Deep Dark Galaxy and Drip Drop Galaxy. The nested Gringills appear in Beach Bowl Galaxy, Sea Slide Galaxy and Deep Dark Galaxy. The swimming Gringills appear in Drip Drop Galaxy.
Giant Eel Outbreak is a mission in Drip Drop Galaxy that highlights the penguins complaining that they cannot fish because the swimming Gringills are eating the fish. One of the penguins mention the Gringills were terrorizing the waters. The players' goals is to defeat all of the Gringills.
Gringill's name is an obvious portmanteau of grin and gill. Grin is to smile broadly which often bares the teeth. Gills are the respiratory organs of aquatic animals.