Pirogusu are enemies from A Link to the Past. They are exclusively found within the Dark World's Swamp Palace, specifically in rooms with shallow water.
In rooms where they appear, Pirogusu will wriggle out of sewer holes embedded in the palace's walls and will quickly swim along the edges of the water. Making contact with a Pirogusu will inflict two hearts of damage. They can easily be defeated in one hit with the Master Sword, but they will continuously respawn from the holes until Link leaves the area.