How do they get oxygen ?

Sharks remove oxygen from the water with their gills. In the gills oxygen that was in the water is absorbed in to the bloodstream. At the same time carbon dioxide is removed from the bloodstream and returned to the water. Fish have an operculum to cover their gills. Sharks have five to seven slits open to the outside. Water passes through the sharks mouth and out through the slits. The heart pumps the blood around the body taking oxygen to the shark muscles, and taking the carbondioxide waste back to the gills.