Because of their pure white colour, belugas are very easy to recognize. They are known as "sea canaries" because of the wide range of noises they make. These range from clicks and squeaks to whistles and mooing sounds. Belugas live in freezing Arctic waters, swimming among floating blocks of ice. They feed on fish and crustaceans found on the seabed beneath the pack ice.

Dolphins

Dolphins, like whales, live permanently in the water. All dolphins have teeth. Most live in the ocean, but some live in rivers. Many dolphins live in groups called pods, which usually stay together for life. Highly intelligent animals, they have good eyesight and exceptional hearing. They call to each other using squeaks and clicks.

Dolphins hunt fish and squid near the water’s surface. The pod hunt fish by working together to round them up. Dolphins are well known for their speed and their acrobatic leaps out of the water, called breaching. This may be to alert other dolphins to the presence of food—or they may do it just for fun.

The humpback whale is a large baleen whale. It has long flippers. Warts, called tubercles, cover its head. Humpbacks often leap out of the water, splashing down on their backs. They feed on krill in polar waters. Humpbacks often make moaning or crying noises. These “songs” may last for hours at a time. Humpbacks catch fish in a clever way. A group of the whales blow a ring of bubbles around the fish. This makes a kind of "net" which traps the fish inside.

Killer whale (orca)

The killer whale, or orca, is the largest member of the dolphin family. It has a tall fin on its back and distinctive black and white colouring. It may grow up to 10 metres (33 feet) long, although it is usually not quite as big as that. The orca preys on fish, penguins, seals, sea lions, other dolphins and whales—even those larger than itself. A fearsome hunter, it is also a highly intelligent animal, peaceful towards humans.

Manatees and dugongs are bulky mammals that live in the water all the time. They have large flippers and flat tails. They live in shallow coastal waters, lakes and rivers of the tropics. Manatees are gentle plant-eaters. Distantly related to elephants, they are sometimes known as “sea cows”. They feed on underwater plants such as seaweed or sea grass. Manatees often rub against each other. They sometimes “kiss” by touching noses.

Porpoises

Porpoises are smaller than dolphins, and have blunt snouts. They usually live alone or in small groups. Most are shy animals that stay below the surface of the water as often as possible.

Seals and sea lions spend much of their time at sea hunting for food. They come out on to land to breed and suckle their young. Most eat whatever they can find, including krill, fish, squid and even birds. The leopard seal even eats other seals. Their flippers help them move through the water at high speed. Some seals can hold their breath under water for half an hour or longer. Sea lions have ear flaps and can get about easily on land. Seals have smooth heads and their ears are not visible. They shuffle about clumsily on land.

The sea otter spends nearly all its life at sea, rarely coming ashore. At night, it wraps pieces of kelp (a type of seaweed) around itself to stop it drifting away with the current.

The sperm whale is the largest of the toothed whales. It grows to up to 18 metres (60 ft) long. It has the largest brain of any animal. It can dive to depths of at least 1000 metres (3300 feet). Very likely, it goes much deeper than that. It preys on giant squid, which live at these great depths. Female sperm whales live together with their young in groups called pods. Males roam solo, or move from pod to pod. Sperm whales can live for 70 years.

The walrus's massive body is covered with thick, tough skin. Underneath, there is a layer of fat, called blubber, that protects it from the cold. The walrus eats clams. It uses its huge tusks to lever them off the rocks. It also eats shrimp, crabs and other molluscs. On summer days, large groups of male walruses gather on Arctic coasts. If there is no room, they will happily lie on top of one another. After half an hour in the sun, their skin turns pink.