Freshwater refers to naturally occurring water on the surface such as bogs, ponds, lakes, rivers and streams, and underground in aquifers and underground rivers. Freshwater's characterized by having low concentrations of dissolved salts. The term specifically excludes seawater and brackish water. Systems Scientifically, freshwater habitats are divided into lentic systems, which are the stillwaters including ponds, lake,swamps and mires; lotic systems, which are running water and groundwater whi… (More on Freshwater)