In the layout of Figure 7a, corresponding to frames N = 7 and 9, analogous concentrations of vorticity A, B and C are identifiable for all levels of submergence h/D. Their form, circulation and position, however, vary substantially. At the deepest submergence (top row of images), vorticity concentration A takes an approximately circular form, whereas at the intermediate depth of submergence (middle row), concentration A is substantially elongated and eventually takes the form of a sequence of small-scale concentrations of vorticity embedded in a vorticity layer. For the shallowest submergence (bottom row), corresponding to surface piercing during a subsequent instant of the wave cycle, vorticity concentration A is dramatically reduced in both the circulation and spatial extent. It initially appears on the upper surface of the cylinder, then migrates in the clockwise direction and, in conjunction with interaction of vorticity concentration B with the cylinder, it eventually takes the form of two distinct vorticity concentrations. Taking an overview of the evolution of vorticity concentration B for varying degrees of submergence, its peak level of vorticity increases with decreasing h/D; at the shallowest submergence, i.e., smallest value of h/D, it takes on a highly concentrated form. Finally, vorticity concentration C appears above the cylinder at the deep and intermediate values of submergence, but is located adjacent to the lower surface of the cylinder at the shallowest submergence. Generally speaking, the effect of decreasing submergence is to retard the orbital motion of vorticity concentration C in the clockwise direction.