On October 29, 2012 Superstorm Sandy (formerly Hurricane Sandy) made landfall in New Jersey. With unprecedented size, extreme central low pressure, and full-moon timing , it created a storm surge that inundated New York City with record-breaking water levels, resulting in tremendous destruction of buildings and infrastructure. All along the East River, large areas of the adjacent boroughs were impacted by Sandy, including flooding of the subway tunnels under the river. When Sandy struck, Verdant Power was operating two acoustic Doppler current profilers (ADCPs) at its Roosevelt Island Tidal Energy (RITE) Project in New York City's East River, measuring water velocities and depth. The East River water speed and level data acquired during Sandy is revelatory, not only indicating the extent and timing of the extraordinarily high levels, but also significant changes to the very sense of the tidal flows. As a Federal Energy Regulatory Commission (FERC) licensee for a commercial pilot project to install up to 30 turbines in the East River, Verdant is keenly interested in the effects such an extreme storm could have on turbines, instruments and navigational aids. This unique observational data provides a valuable insight for Verdant Power and the marine and hydrokinetic (MHK) industry.In this paper, Verdant first presents the East River data collected during Superstorm Sandy, indicating what actually happened during the storm. The potential for yet more extreme water levels with a different storm timing relative to the astronomical tides is then examined. Finally, of interest to a kinetic hydropower developer, the data is analyzed to estimate how a different storm timing could affect the water velocities through the river. These findings are related to the design criteria for Verdant's equipment and the potential impact of an extreme storm on a commercial array of kinetic hydropower turbines.