The first features that most people notice about sharks are their streamlined, torpedo-like shaped body, fins, and sub terminal mouths (under their heads). A shark’s body is adapted to living in the ocean, where every tail movement requires hard work to move through the dense medium. Many sharks need to keep swimming to breathe, so it is very important that there is nothing to prevent the shark from moving efficiently. This is the reason why their fins, tail, and scale alignment are adapted to allow water to flow easily over their body, reducing drag and energy consumption. Fast swimmers such as mako and silky sharks have a streamlined body shape and are considered hydro-dynamically silent. The ability to pass through water with the least resistance is achieved by the shark's rough skin.