A generator can convert the energy from subsurface currents or undertow into electricity. The generator has a submergible electrical coil adapted to allow water propelled by subsurface currents to enter and flow axially through the coil. The electrical coil is supported above a sea floor in substantial alignment with the subsurface currents. A magnetic shuttle is mounted to longitudinally reciprocate in the coil, driven by water flowing through the coil. Additionally, a plurality of electrical coils can be submerged above a sea floor. Magnetic shuttles are placed separately into a corresponding one of the coils to longitudinally reciprocate, driven by water flowing through the coils.