There are indications that submerged bulk anodes alone provide some protection in the splash zone, albeit not as much as when combined with either thermal-spray or zinc jackets. Experimental results as well as calculations were used to evaluate the extent of cathodic protection that may be achieved in marine substructures by means of submerged magnesium bulk anodes (SMgBA). To investigate the extent of any contribution of SMgBA in protecting the above-waterline zone, two substructure piles were instrumented with SMgBAs. In addition, a substructure with a SMgBAs was modeled using 1D and 2D finite difference models, the results compared with the field measurements, and the utility of cathodic protection using SMgBAs alone projected.