Because they are constantly swimming against the current of a river where as sea otters float around...kinda.
It helps it swim faster mate
Researches have shown that hudson river is actually the safest river to swim in the United states. As long as you do not swim in the deep places, you are fine.
Sea otter are nekton and plankton; they can float and swim.
Freshwater otters get their water from freshwater sources. Thus, species like the North American river otter (Lontra canadensis), the Eurasian river otter (Lutra lutra), and the Asian small-clawed otter (Aonyx cinerea) drink from the same rivers and lakes in which they swim. The sea otter, on the other hand, is specially adapted to its saltwater habitat. The sea otter's large kidneys process the saltwater that the otter drinks from the ocean, allowing the otter to live without need of freshwater.
A North American River Otter can swim at speeds of up to 7 miles per hour (11 km/h) in the water. They are agile and efficient swimmers, using their webbed feet and sleek bodies to move gracefully through the water in search of prey.
otters line near river, streams and oceans. so yes they swim.
a curved tail to swim faster
They can swim 5.6 miles per hour underwater.
It was really fun to watch the otter swim and do aquatic acrobatics.
sea otter
Otters are mammals but they can swim and live in water.
yes because there is a certain type of otter called the river otter