Fur and blubber
Australian Fur Seals are called fur seals because they have an under fur which is protected by longer guard hairs. Sea lions do not have the under fur, they only have the guard hairs. The fur on a fur seal is thick and traps a layer of air so the seal's skin does not get wet.
Under the skin is a thick layer of fat called blubber. The thick hair and blubber help to keep the seals warm when they are in the cold sea and when they are exposed to the elements when resting on land.
When seals are swimming their fur presses down making them stream-lined and quick swimmers.
Australian Fur Seal
Sea Lion
Extra thick blubber helps keep the Harp Seal warm as they live in the cold North Atlantic and Arctic oceans. Harp Seals spend most of their life in the water as it is warmer than on the ice. Newborn pups rely on both their blubber and thick white fur coat to keep them warm from the icy cold extremes on land.