Best time to see: late Oct to end Apr

Key facts

The largest of the divers seen off the Essex coast in winter, and very occasionally inland on reservoirs

Breeds in Greenland, Iceland and N. America

Recognition

In winter, dark above and pale below, with large greyish bill; male up to 90 cm, female 75 cm

Swims on the sea off the coast, singly or in small groups, with head and bill held horizontal

Dives frequently and stays down for minutes at a time, eating fish and shellfish