This allows for absorbing the shock of the impact of ocean waves, hauling out on ice or rocky coasts, or executing agile maneuvers to capture prey at sea. Pinnipeds are less modified for aquatic life than are the wholly aquatic cetaceans. Like the cetaceans, pinnipeds have a thick coat of subcutaneous blubber to provide energy, buoyancy, and insulation, but most also have a hairy coat to protect them from sand and rocks when ashore. This underfur traps small bubbles and keeps the skin dry, while the stiffer guard hairs protect the body from abrasion. Molting in pinnipeds usually occurs after the breeding season and is most spectacular in the elephant seals and monk seals, whose outer layer of skin is shed in patches along with the fur.
Pinnipeds are clumsy on land, but in the water they are skillful divers and swimmers.
They swim by means of the flippers and by sinuous movements of the trunk. This phenomenon, known as bradycardia, develops more rapidly and lasts longer as the seal grows older. During the dive, the seal's peripheral blood vessels are constricted and circulation is reserved for the heart and brain, thus reducing oxygen consumption by one-third. In addition, pinnipeds have a high tolerance for carbon dioxide and lactic acid build-up in the blood. When the seal surfaces, its heart regains its normal beat within 5-10 minutes, and the blood is reoxygenated by the increased beat and a few deep breaths of air.