There are a large number of sites in the world's oceans and rivers that can provide a significant, viable, and cost effective source of renewable energy. Many are strategically located close to populated areas where these sites can be used to harness energy using ecologically benign hydrodynamic technology. A hydrodynamic array comprises multiple hydrodynamic elements for producing electricity by the motion of ocean tides or river currents and forces acting on the hydrodynamic array, which is immersed in ocean tides or river currents and which is in motion relative to the ocean tides or river currents.