Sailor's Grunt

Found in schools during the day, dispersing at night , foraging for food, over open, shallow coastal reefs.
They feed nocturnally on small fish and molluscs.

In some areas of the world 'Grunts' are better known as 'Sweetlips' distinguished from other species by their very large rubbery lips.
'Grunts'because they "grunt," the grunting sound is produced by their flat teeth plates rubbing together and this is amplified by their air bladders.
Found either singly or in schools hovering or motionless over the reef during the day, becoming nocturnal predators.