Sea otters

Officially called Enhydra lutris, and unofficially known as the cutest creatures that float, the sea otters in today's image are found in Sitka Sound, Alaska, in the United States. Groups of males or females (sometimes with puppies) are appropriately called rafts. Male rafts are usually larger and can number more than 1,000 people. Their floating bodies are like literal rafts, functioning as cradles, dining tables, or any kind of solid surface. This is useful because otters spend most of their lives in the water, even in the sea.

While they appear to be living, frolicking, caring for and diving carefree, they also play an important role in keeping their aquatic ecosystems healthy. Otters keep the giant kelp forests of the Pacific Ocean healthy by eating sea urchins, which would otherwise decimate kelp, an important habitat for many fish and other marine animals. Otters also eat crabs, crustaceans, cuttlefish, and other invertebrates. An otter's calorie requirement is enormous. It has to eat a quarter of its body weight each day to satisfy its cold-water metabolism.

The key to an otter's aquatic lifestyle is its coat, the thickest of any mammal, so dense that its skin never really gets wet. Otters need all those hairs to stay warm because they don't have a layer of mud like other marine mammals. Although they can walk on land, they almost never find the need or desire to do so, even if the nap time is. When they're ready to sleep, they wrap themselves in a strand of kelp to prevent them from drifting away and let their floating bodies float to keep them afloat.