All ducks have webbed feet. Most live in aquatic environments, thus the need for the webbed feet. Male ducks are generally more brightly colored than the females. Some ducks are vegetarians, others eat such things as fish, insects, and snails.
Most ducks prefer fresh water.
You will find them in many riparian areas, from rivers and ponds, to coastal marshes. A duck track in mud. The webbing on the feet is clearly visible in this track. This helps the duck to swim. It probably also helps the duck stay on top of the deep mud frequently found in the riparian areas these birds inhabit.