How many otter species live mainly in freshwater habitats?

Of the 13 recognized otter species, 11 are generally classified as freshwater or "river" otters.12

While these species are primarily associated with freshwater ecosystems, it is important to note that the term "river otter" is a broad categorization for members of the genera Lontra, Aonyx, Hydrictis, Lutra, Lutrogale, and Pteronura. These animals are often opportunistic and may forage in various environments, including land and coastal areas.3

The remaining two species are strictly marine: the sea otter (Enhydra lutris) and the marine otter (Lontra felina). Although the marine otter is biologically a freshwater-type otter that has adapted to occupy marine environments along the coast of South America, it is distinct from the 11 species that live mainly in freshwater habitats.42