This round-headed diving duck is identifiable by its distinctive features. Males have a black breast, medium gray back, white sides, and yellow eyes. Their head appears black with a greenish sheen in good lighting, never showing a purplish hue. Females are brown overall, with a grayer body in winter, a white patch at the base of the bill, and yellow eyes. It closely resembles the Lesser Scaup but can be distinguished by its smoothly rounded head without a tall peak, puffier cheeks, a more extensive white stripe on the wing in flight, and a larger, broader bill. It can also be similar to immature male and female Tufted Ducks, but it has a smoothly rounded head and a more extensive white patch at the base of the bill in females. Often found in flocks with other Aythya ducks, it tends to prefer saltwater bays and coves but can also be found in freshwater.