Sea otters have over one millions hairs per square inch on their body. These thick coats are necessary for them to keep them warm in the cold ocean water because they lack blubber, a thick layer of fat other marine mammals possess. The sea otter's coat was at one time considered an extremely valuable pelt for clothing, and the little guys were almost hunted to extinction because of high demands for it. Because of their thick fur, they are also seriously effected by oil spills. The oil can prevent the otters from blowing air into their fur, which works like insulation to help them keep warm, and so sea otters covered in oil will often freeze to death.
Sea otters are also incredibly cool because of they way they feed.
This is actually a form of tool use. Due to pollution, habitat encroachment, and previous hunting, the sea otter population in California was for awhile on the brink of extinction. The good news is the population has made a wonderful recovery, and there are now over 2000 sea otters in California. The bad news is the population appears to once again be declining at a rate of over 200 deaths per year, and if this pattern continues, sea otters may no longer be found on the California coast 10 years from now.