A round-backed, round-headed duck with a stubby bill, typically with dark grey females and immatures far outnumbering adult males.

Although not a sawbill, the Goldeneye is similar in many ways to the scarcer Smew; indeed the two occasionally hybridize. Goldeneyes tend to keep apart from other ducks such as Tufted Ducks in winter, forming separate feeding and roosting groups. It may seem that only a few are present, as they dive so constantly, but if disturbed they gather together and may fly off in surprising numbers. They are usually nervous and quite difficult to approach.