The littoral zone describes the area of the coast exposed during low tide down to the lowest area influenced by tidal action (usually around 100 meters deep). In freshwater ecosystems, the littoral zones occur on the edge of large lakes and rivers, usually with extensive areas of wetland. The region is characterized by large variations in temperature, salinity, and turbidity (amount of suspended material in the water). Since this is the transition between water and air, organisms in this habitat are adapted to both aquatic and aerial atmospheres, and can adjust to the rapidly fluctuating conditions of this shallow zone. The crocodiles in the image above represent one such species.