The skin of fast-swimming sharks is proposed to have mechanisms to reduce drag and delay flow separation. The shortfin mako Isurus oxyrinchus is one of the fastest and most agile ocean predators and would benefit from minimizing its pressure drag by controlling flow separation. The skin of shortfin makos is covered in teeth-like denticles with lengths on the order of 0.2 mm. Recent biological studies have shown the bristling angle of these denticles to exceed 50° in locations likely to experience separation first. It is proposed that the reversing flow that occurs near the onset of separation activates denticle bristling. Once activated, the scales would impede the development of a more global separation event over the shark by stopping the reversing flow from travelling further upstream and causing interactions within the boundary layer that allow it to stay attached longer. Real shark skin samples are exposed to reversing flow and the interactions with the scales are documented with a specialized camera setup. The camera setup provides high magnification while still providing a large enough depth of field to visualize scale movement. It is shown that reversing flow indeed interacts with the scales and causes bristling in flank region specimens. Because it is not possible to test at the swimming speeds of the real mako in the University of Alabama water tunnel, a biomimetic scale array model is used in the experiment to study the boundary layer, Re stress, and cavity structures over the shark skin. It is shown that the introduction of the scales in the turbulent boundary layer yields a positive benefit in the flow by brings higher momentum fluid toward the surface. An examination of the cavity structures shows cavity vortices in most cases, with the notable exception being the first cavity in the turbulent boundary layer case which shows no average core vortex and instead shows an outward trend of fluid motion toward the boundary layer above. These results indicate the possibility of shortfin mako scales to control flow separation.