Using seawater as the electrolyte and a shark fin clipping as the cathode, voltages measured closely correlated with the standard reduction potential of the metal under test. SharkDefense now hypothesizes that a net positive charge from the cations produced by the electropositive metals accumulate on the electronegative skin of the shark. The net increase of the charge on the shark's skin is perceived by the ampullae of Lorenzini, and above 1.2 eV potential, aversion is produced.