Fresh Water - Brackish Water - Salt Water
Freshwater ecosystems are a subset of Earth's aquatic ecosystems. They include lakes and ponds, rivers, streams and springs, and wetlands.
Brackish water, or briny water, is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers.
Salt water ecosystems are among the largest of Earth's aquatic ecosystems. They include oceans, salt marsh, estuaries, lagoons, mangroves and coral reefs, the deep sea and the sea floor. Marine waters cover two-thirds of the surface of the Earth.