An intertidal zone, also known as a seashore, foreshore, or littoral zone, is an area that is above the water level at low tide and underwater at high tide. It is the central part of the peritidal zone, which extends from above the highest tide level to below the lowest. It can be just a narrow strip or it may include many meters of shoreline with shallow, sandy beach slopes and can also include wetlands and steep, rocky areas.
Intertidal zones, especially those of oceans, are often harsh environments with extreme and constantly changing conditions. This includes periods of inundation from the tides and dry periods between inundations. Salinity in oceanic intertidal zones can range from greater than that of sea water due to evaporation from tidal pools to fresh water from rainfall. There is typically high exposure to intense sunlight, both direct and reflected from the sand and water. Temperatures can swing back and forth rapidly between very hot with the daytime sunshine exposure during dry periods to very cold from the cold or freezing tidal water especially at night. Adding further to this harshness is the mechanical action from waves and the exposure to predators.