Seals" lives are adapted to life in the water. However, they also spend time on dry land. This is why seals are less adapted to water compared to other marine mammals. Cetacea, for instance, live in the water permanently. Seals have adjusted to living in and under the water, which is very different from living in the open air. The adjustments have made it easier to survive and move about in the water.
Mammals are unable to extract oxygen from the water. This means that seals must come up to the surface regularly to breathe. In order to stay under water for a longer period of time, for instance to gather food, a seal has developed many different ways of saving oxygen (Read more in section SWIMMING &DIVING). Water conducts heat more efficiently than air, which is why water is better for keeping a seal"s body warmth up (Read more in section FUR & BLUBBER). Water has a higher density than air. This has an effect on movement: Seals use more energy while they swim than land animals use while moving around on land. However, water also supports the body, which has consequences for the build of marine mammals" bodies. You can see this in large whales: Because the water provides buoyancy, there is no natural limit to its size. Sea mammals protruding limbs have been minimized to reduce the surface that is exposed to the cold water