Shark skin is not made up of traditional fish scales.  Rather, they have minature teeth similar to shark teeth in general that interlock (see the close up picture above).  These scales are called “dermal scales”.  Recent hydrodynamic research has show how these scales actually bristle like fur and push the water down the shark more efficiently and with less drag.  Check out this incredible talk by Bob Hueter about this miraculous research by clicking .  Also, some zoologists suggest that early ancestors of sharks developed shark skin before developing teeth and that shark skin is the basis of teeth formation for all modern day animals. 

So the next time you pet a shark, make sure you go head to tail!