Oysters can be found in shallow waters, along the shores, attached to rocks or shells.  An oyster opens its shell to eat and closes it when it is disturbed or an enemy is approaching.  An oyster also closes when the tide goes down and it is exposed to the air.  Surprisingly, and oyster has no head but it has a mouth.  It survives by straining food out of the water through its gills.  It takes in water and with it food particles.  Food particles stick to a sticky substance which passes the food along to the  mouth.  As an oyster grows its shell grows!  On the inside of the shell a smooth surface is formed called the mother-of-pearl.  If a grain of sand gets under the surface by the shell a small pearl is formed.  Some oysters release eggs into the oceans while others may keep them inside the shell until the eggs hatch.  After the eggs hatch the young swim around freely, but soon they swim to the bottom to find an eating place and here they cement themselves for the rest of their life.