Dippers are members of the genus Cinclus in the bird family Cinclidae. They are named for their bobbing or dipping movements. They are unique among passerines for their ability to dive and swim underwater.
Dippers are found in suitable freshwater habitats in the highlands of the Americas, Europe and Asia. In Africa they are only found in the Atlas Mountains of Morocco. They inhabit the banks of fast-moving upland rivers with cold, clear waters, though, outside the breeding season, they may visit lake shores and sea coasts.
Unlike many water birds, Dippers are generally similar in form to many terrestrial birds, but they do have some morphological and physiological adaptations to their aquatic habits. Their wings are relatively short but strongly muscled, enabling them to be used as flippers underwater. They have dense plumage with a large preen gland for waterproofing their feathers. Relatively long legs and sharp claws enable them to hold onto rocks in swift water. Their eyes have well-developed focus muscles that can change the curvature of the lens to enhance underwater vision. They have nasal flaps to prevent water entering their nostrils.
Source: en.wikipedia.org/wiki/Dipper -02.10.2010
This is real, too: a songbird which is able to swim and even to dip easily.
On top of that the Dipper is so resistant against coldness, that sometimes it exists above the timber line.