Many seakeeping analyses are performed using idealized wave statistics from a vessel’s expected operation area; however, widely available wave forecast and hindcast data present an opportunity for digitalization in the marine industry through time-and-place specific response predictions. To better understand the effect of wave data source selection on these predictions, quantification of the differences between results generated using different sources is required. Two locations off the coast of Alaska were selected for analysis over a one-year period. Data were used from the NOAA WAVEWATCH III Production Hindcast, the EU’s Copernicus Marine Environment Monitoring Service Ocean Waves Analysis and Forecasting Product, and nearby National Data Buoy Center buoys. Frequency-domain predictions of a ship’s heave, pitch, and vertical bending moment responses revealed significant disagreement between wave data sources. More pronounced disagreement was found for the vessel’s cumulative fatigue damage, highlighting the importance of accurate wave data for time-and-place specific analyses.