Common seals are speckled, with a small round head and big dark eyes. Grown-ups are about 1.5 metres long. They have a thick layer of fat called 'blubber' under their skin to keep them warm in the cold Danish sea. They can dive for up to half an hour without taking a breath.
Seals are brilliant swimmers but clumsy on land. On a beach they hump along like a furry caterpillar. They prefer to rest on small sandbanks that appear when the tide goes out, where they can flop down and snooze in safety. From a distance, a sandbank full of seals looks like a row of grey sausages.
Seals talk to each other with little grunts, snorts and barks. Mum seals know their babies by voice alone. A baby seal - called a pup - is born on the sand and can swim almost straight away. The pup stays with mum for about a month, drinking her very fatty milk, before learning to catch its own fish.
Seals eat fish, octopus and small crabs. They have amazing whiskers - so sensitive that a seal can find a fish in the dark just by feeling the tiny ripples it makes in the water. Sometimes a seal will follow a boat to see if there are any easy fish to be had.