Most annelids in the taxonomic class are marine.

hirudinea

oligochaeta

polychaeta

all of the above

Polychaeta - over 8000 species of annelid worms that are mostly marine. 
Oligochaeta - about 3100 species of annelids that includes earthworms and many species that live in freshwater. 
Hirudinea - about 500 species of marine, freshwater, and terrestrial worms commonly known as leeches. 

Hope this helps.