The term water bird, waterbird or aquatic bird (not to be confused with wading birds) is used to refer to birds that live on or around water. Some definitions apply the term especially to birds in freshwater habitats, though others make no distinction from birds that inhabit marine environments. In addition, some water birds are more terrestrial or aquatic than others, and their adaptations will vary depending on their environment. These adaptations include webbed feet, bills and legs adapted to feed in water, and the ability to dive from the surface or the air to catch prey in water.
The anhinga does not have waterproof feathers. As a result it can dive and search for underwater prey, including fish and amphibians. It can stay below the surface more easily and for longer periods of time.