Otters live in most areas of the world ! The only continents where otters do not live are Australia and Antarctica. Most otters can be found in freshwater streams, rivers, lakes and coastal areas.
The Sea Otter lives in the ocean and is in all ways a marine mammal.
Source: Otters: An Action Plan for their Conservation; IUCN/SSC Otter Specialist Group; published 1990 (the Year 2000 update is underway and information will be updated when available)