River otters will live in all kinds of water, not just rivers. They like to have fresh water where they can swim, hunt for prey, and play.
On land, they use their senses of smell and sight to find they prey. They eat fish, amphibians, crustaceans and if they can catch them, small mammals.
When they dive in the water, otters use their sensitive whiskers to find prey.
River otters like to slip and slide in the mud and snow.
Locally, check out the Blackstone River Bike Trail for otters. I have seen them there twice.