Water is a viscous medium and therefore presents considerable resistance to animals moving through it. It is not surprising, therefore, that fishes have evolved a variety of mechanisms to minimize the cost of swimming. Variations in body shape, fin shape and location, and swimming style. Fishes also can utilize vortices in their environment to reduce the cost of swimming (Liaoet al. 2003). These vortices may be created by either water moving past an obstacle or by the movement of other fishes,such as those in a school. By carefully positioning themselves fishes can use the vortices to “slalom” ahead while reducing the activity of trunk muscles normally used in propulsion, thereby conserving energy.