There are over a dozen different otter species in the world, but only two in North America—the sea otter and the North American river otter. The most obvious difference between them is that one lives in the ocean and the other lives in fresh water, but there are a few other things that make each species distinct.

Sea otters are much bigger than river otters. They weigh anywhere from 45-90lbs while little river otters only weigh about 20 lbs. Sea otters have a short, flat tail and river otters have one that is long and round. Sea otter fur is much more dense, giving them that super furry face that everyone loves. River otters look more like weasels. 

Fun fact: Sea otters have the densest fur of any animal. This dense fur is what keeps them warm since they don’t have a thick layer of blubber like walruses, seals, and sea lions.

River otters swim on their stomachs while sea otters spend most of their time floating on their backs. River otters spend a good chunk of their lives on land as they mostly use water to travel and hunt. Sea otters, on the other hand, spend their lives almost exclusively in the water; they even give birth in the ocean! They also tend to only have one pup at a time while river otters often have four!