When water passes over the gills capillaries in the sharks blood absorb the oxygen from the water through diffusion. Sharks have 5-7 pairs of gill slits located on the sides of their heads and they do not have gill covers like most fish.Water must continually flow across these slits in order for the shark to breathe. This can be accomplished by the shark's swimming, by it standing still in a current. Tiger sharks are one of the special sharks that have spiracles which are gill slits located just behind the eyes. They supply oxygen directly to the eyes and brain. The reason Tiger Sharks have spiracles is because them being bottom dwelling sharks. Tiger Sharks use body posture to communicate with one another since they are one of the most aggressive sharks.