Eels fall into one of two categories: short fin and long fin. Depending on which class they are grouped into, eels vary in size and ideal habitat. Some live in freshwater, while others prefer salty marshes and ocean habitats.
Long fin eels live primarily in rivers and lakes along coastal areas, but they can also live inland away from oceans and salty environments. These eels are much larger than short fin eels, and the most prominent member of this family is the moray eel. Short fin eels, on the other hand, live primarily in freshwater habitats, such as lakes and bays. Like long fins, short fin eels are long and narrow in build.