From WordNet (r) 3.0 (2006) [wn]:
freshwater
n 1: water that is not salty [syn: fresh water, freshwater]
[ant: brine, saltwater, seawater]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Fresh-water \Fresh"-wa`ter\, a.
1. Of, pertaining to, or living in, water which is not salty;
as, fresh-water geological deposits; a fresh-water fish;
fresh-water mussels.
[1913 Webster]
2. Accustomed to sail on fresh water only; unskilled as a
seaman; as, a fresh-water sailor.
[1913 Webster]
3. Unskilled; raw. [Colloq.] "Fresh-water soldiers."
--Knolles. Fresnel lamp