The correct answer to this question is blubber. Also known as adipose tissue, blubber is thick fat. All marine mammals, like whales and seals, have it under their skin. The only place it won't appear is on their flukes, flippers, and fins. Blubber is not only just a layer of skin, but it has many essential functions. For one, it insulates the mammals.
Marine mammals live in icy waters, so the blubber keeps them warm. Another feature is that it stores energy. This is important because the mammals won't have to search for food for a long time, being that they already have a source.
Whales can weigh up to 180 tons, which is 360,000 pounds and at least 50% of that weight is attributed to fat. That is a lot of fat for an animal; however, the blubber is an essential piece of the entire whale. Depending upon the species and what part of the earth they populate the blubber factor can be anywhere from one inch to eleven or so inches thick.
Blubber on a whale provides the animal with the proper insulation protecting their organs from injury, the environment, and energy storage. The brain, fins, and tale take part of the weight, along with their organs. Whales float because of their high percentage of lipids, which the blubber contains along with the fat.