Percentage of fish entraining on horizontally oriented cylinders of various diameters with increasing flow speeds. Cylinder diameters are represented from smallest to largest as geometric symbols: diamonds, squares, triangles and circles, respectively. Fish have a preferred range of turbulence, shown by the fact that intermediate diameter cylinders cause the most fish to entrain across the widest span of current speeds. Fortunately, the hydrodynamic environment behind two members in a school can be approximated by the drag wake of a bluff body in flow. This is because a drag wake is created between two parallel thrust wakes . Studies strongly suggest that fish can benefit energetically from swimming in drag wakes by capturing the energy of discrete vortices , so by extension it is reasonable to predict that individuals in a school can also benefit from vortices. Future investigations to visualize flow between two tail-sized flapping foils would lend strong support to the hypothesis that fish can benefit from vortices in a three-dimensional schooling environment.