Fish can move in all directions. Because the function of the muscles attached on either side of the spine. The contraction of the muscles of one side starting from the head to the tail. And a wag of the fin. The head and tail to one to one. Pectoral fin and pelvic fin which is comparable to the front legs and the rear legs of livestock, respectively.This pair fins are help the fish to move up and down in the vertical. The movement of the fish is S-shaped. The fish are flat shape slender with mucus, making the fish moving in the water well. It reduces the friction of water while moving. But the shape and may make the body of the fish is more likely to tip over or roll easily.