Living things along this rugged, rocky shore endure many biological stresses. Rocks don't give plants or animals much protection. There is summer heat, winter freezing, the drying force of air, and the diluting power of rain. The rockiness and irregularity of the coast leads to great variations in water level between high and low tide. Many inlets become shallow at low tide, providing habitats where animals can hide and plants can flourish. Tidal pools form wherever water is trapped and left behind by the receding tide. The tide pools experience extreme fluctuations in temperature, salinity, and oxygen content. On any given rock, living indicators detail precisely where the water level rests at both high and low tides. From top to bottom, this tidal zone can be from twenty to forty feet in height.