A group of baby ducks is commonly referred to as a brood or a clutch. When they are swimming together, they are often called a raft of ducklings. These terms are used to describe the young ducks when they are still in the care of their mother.
Ducklings are known for their strong bond with their mother and their tendency to stay close to her for protection and guidance. This behavior is why the terms brood and clutch are often used, as they emphasize the close-knit nature of the group.