The cornea is flattened, and the pupil is capable of great enlargement to enable better sight in dark water. The neck in pinnipeds is generally thick and muscular, yet quite flexible. A reduction in the interlocking processes of the vertebrae enables these animals to bend backward to a greater degree than most other mammals. The overall design of the body is fluid, with great power and grace evident in the movements. 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.