Lagoons are shallow coastal bodies of water separated from the ocean by a series of barrier islands which lie parallel to the shoreline. Inlets, either natural or man-made, cut through barrier islands and permit tidal currents to transport water into and out of the lagoons. Because lagoons are characteristically shallow, they are strongly influenced by precipitation and evaporation, which results in fluctuating water temperature and salinity. Lagoons can also be fragile ecosystems susceptible to pollution effects from municipal, industrial and agricultural runoff. Lagoons are classified into 3 main types: leaky lagoons, choked lagoons, and restricted lagoons.