1. A streamlined body is one which is pointed at the ends and broad in the middle. When such a body travels through a fluid or gaseous medium it exhibits minimum friction or resistance. A body shape which is streamlined helps cut against the friction created by the medium around the moving body.
2. Streamlined body lowers the friction drag between a fluid, air or water and an object moving trough that fluid. Drag is a force that slows down motion. Streamlining reduces the surface area of the moving object.
3. Streamlining reduces friction of movement to a minimum thus decreasing overall drag. Fishes can save energy while swimming because of the streamlined body.