This order contains large numbers of fowl-like or goose-like birds commonly known as waterfowl. These birds live near water or temporarily go into the water. They have broadened bills containing many tactile nerve endings and filtering ridges at the edges used for filter feeding through the bottoms of lakes, rivers, ponds and occasionally oceans. Their legs are short and, with the exception of screamers, they have webbed feet. The body is well supplied with down and oily feathers. Most are strong flyers. They are full bodied, long necked, swimming or semi-aquatic birds.

The unspotted eggs are light in color. The young are precocial, have dense downy plumage and are capable of locomotion. The hatchlings are tended to by one or both parents, but are capable of leaving the nest on hatching or soon after.

Some waterfowl are omnivorous, while others feed exclusively on algae and some are herbivorous grazers. Most are fresh water birds, although a few maintain a maritime existence. Although a few species are solitary, most are highly gregarious and flocking is instinctive. Geographically, waterfowl are found on every continent but Antarctica.

The order is divided into families depending on the presence or absence of horny lamellae in the bill. The two families are Anhimidae (screamers) and Anatidae (ducks, geese and swans).