Aquatic organisms live in an abundance of water all round the year, and there are factors such as pH, salinity and chemical composition of water that determine the kind of plant and animals that would thrive in a specific area. These organisms are adapted to live either in freshwater or saline water. Those organisms which are adapted to live in a wide range of salinity are known as euryhaline, while those which can withstand only a narrow range of salinity are called stenohaline.