Quantifying the hydrodynamic motions of a floating facility is critical for ensuring its safe and efficient operation. The ability to obtain estimates of the motion response charactersitics using a numerical approach to estimate the seastate is particulary attractive for sites in which limited observational wave data are available. Validation of such a numerial approach using full-scale data is however, desirable in order to establish its accuracy and limitations. To this end, this paper presents a case study where numerical estimates of the dynamic motions of a drillship were validated using high quality dynamic motion records acquired during the drilling campaign. The model comprises a hindcast of the directional wave spectra and numerically derived hydrodynamic response characteristics of the ship. The performance of the model is evaluated using a range of selected seastates which were observed during the drilling campaign. It is demonstrated that reliable estimates of the motions of most interest for a drilling operation can generally be obtained, thus providing support to the use of the provided numerical approach for conducting operability assessments for floating facility planning purposes.