Their sense of smell is most accurate and great whites can detect a single drop of blood in ten billion drops of water. They possess an “ear stone” which helps the animal position itself in the water depending on the direction it is swimming.[18] Sharks also utilize excellent vision with retinas divided into two areas for daylight and nighttime swimming, and protect them by rolling them backwards into the skull before biting. One of their most interesting senses relates to their touch and electro-reception. A series of pores in the shark’s nose allow them to detect electromagnetic fields and sense animal vibrations in the water, as well as accurately navigate through the open ocean.[18] The great white becomes an adult about nine years after its birth. The growth of the great white shark is about 25-30 centimetres per year and they grow to an average size of 4.5 meters. The largest can be as much as 6.4 meters in length. Their liver, a delicacy to killer whales, can weigh up to about 24 percent of its own body weight.[19] The Great white shark (Carcharodon carcharias) is the only representant of the genus, and the only living species.