How do you differentiate between fresh and salt water?

Freshwater and saltwater can be differentiated primarily by their salinity levels. Freshwater typically contains less than 1% salt, making it less salty than seawater, which has an average salinity of about 3.5%. Additionally, freshwater sources include rivers, lakes, and streams, while saltwater is found in oceans and seas. The presence of various organisms and plants adapted to these environments can also help in distinguishing between the two.