zsl-edge-of-existence:

Unlike seals, whales, and other such marine mammals, sea otters do not have blubber (a thick layer of subcutaneous fat) to keep themselves warm in cold ocean waters.  Instead, sea otters are insulated by a remarkable coat of fur.  At 150,000 strands of hair for each square centimeter of skin, the sea otter’s fur is the densest of any animal in the world, and keeps cold water from even touching the animal’s skin.  The fur must be kept scrupulously clean in order to retain its insulating properties, and so sea otters spend a great deal of their time grooming and washing.  Their skin is so loose that the otter can easily reach and groom every square inch of its body.  The fur will also trap air bubbles between the outer “guard” layer and the undercoat, which not only helps keep the otter warm but will aid in buoyancy.  In fact, a newborn sea otter’s fur will retain so much air that, after careful grooming by its mother, the baby literally cannot sink; it bobs in the water like a cork.