Medium-sized, chunky, oddly shaped, big-billed duck. Long tail is sometimes cocked up to produce a distinctive silhouette. Breeding male has a black head, rufous body, and blue bill. Female and non-breeding male are dark brown with white head stripes. Prefers freshwater wetlands such as lakes, ponds, and lagoons, though sometimes found on saline lakes. Floats low on the water. Rarely seen in flight; prefers to dive to flee disturbance. Odd shape is unlike any other duck in its range. Colorful breeding male is distinctive.