A fun fact about the sea otter, an aquatic member of the weasel family, is that despite being the smallest of all marine mammals, they actually have the thickest fur of any other marine mammal. The sea otter's coat can average 850,000 to 1,000,000 hairs per square inch. This coat helps insulate them against the cold and makes them waterproof.
Sea otters spend most of their time in water and are often seen floating on their backs. In this position, they not only sleep, wrapping themselves in kelp, but they also eat, cracking open shellfish that they have caught with the help of a rock gathered from the ocean floor. In this position, they can also nurse and nurture their young. Because sea otters give birth in the water (the only type of otter to do so), the ability to carry young before they learn to swim on their own is necessary for survival. In the early 20th century, these animals nearly reached extinction. At that time, only 1,000 to 2,000 sea otters remained on Earth because they were so widely sought after for their valuable fur coats. As of August 2014, 100,000 to 150,000 sea otters are protected by hunting laws.