They don’t come to the surface for air like some marine mammals, because sharks are fish. Like any other fish, they rely upon their gills to allow them to breathe while under water.
Identification: The Great White Shark is often of immense size and girth. Conical snout with broad jaw containing large, serrated, triangular teeth. Round, blue/black eye with no nictitating layer. Gill slits long. Ventral tips of pectoral fins black or dark. Occasional black spot on pectoral axil. Second dorsal and anal fin small. Well developed caudal keel. Caudal fin lunate and only slightly asymmetric. Upper body grey or blue/grey with distinct ragged demarcation to white or pale underside.