A total of 13 otter species are found worldwide, including 7 distinct genera. Otters are mostly dependent on freshwater habitats, but 4 species are either residents or occasional inhabitants of marine environments. Of these, only 2 species are adapted to a strictly marine existence: the sea otter (Enhydra lutris) distributed along the North Pacific Ocean and the marine otter (Lontra felina) found in the southeast Pacific Ocean, and also associated with kelp and seaweed.
However, the only two otter species native to the Oregon coast are the river otter and sea otter. While lone wandering sea otters are seen occasionally in Oregon, most sightings turn out to be river otters.