Which two otter species are strictly marine?

The two otter species that are considered strictly marine are the sea otter (Enhydra lutris) and the marine otter (Lontra felina).1

Both species rely exclusively on marine prey for their diet. While the sea otter is highly adapted to life in the open ocean and can remain at sea for several days, the marine otter is typically found within 100 to 150 meters of the coastline, often sheltering in rock cavities or sea caves along the shore.12