This study demonstrates a site resource assessment to examine the temporal variation of the current speeds, current directions, turbulence intensities, and power densities for a tidal energy site in the East River tidal strait. These variables were derived from two months of acoustic Doppler velocimeter (ADV) measurements at the design hub height of the Verdant Power Gen5 hydrokinetic turbine. The study site is a tidal strait that exhibits semi-diurnal tidal current characteristics, with a mean horizontal current speed of 1.4 m s−1, and a turbulence intensity of 15% at a reference mean current of 2 m s−1. Flood and ebb flow directions are nearly bi-directional, with a higher current speed during flood tide, which skews the power production towards the flood tide period. The tidal hydrodynamics at the site are highly regular, as indicated by the tidal current time series that resembles a sinusoidal function. This study also shows that the theoretical force and the power densities derived from the current measurements can be significantly influenced by the length of the time window used for averaging the current speed data. Furthermore, the theoretical power density at the site, derived from the current speed measurements, is one order of magnitude greater than that reported in the U.S. national resource assessment. This discrepancy highlights the importance of conducting site resource assessments based on measurements at the tidal energy converter device scale.