The ability to derive the directional wave spectra directly from the motions of a floating facility can be of significant value to offshore industry, particularly for sites where reliable observations are not available. This study employs new full-scale measurements of the dynamic motions of an operating drillship to evaluate the performance a parametric model to estimate the directional wave spectra at a swell dominated region. The drillship was dynamically positioned and operated at a constant draft which reduces the inherent uncertainties in the model. The model was applied to a range of interesting wave states, including multi-modal swells and the results were compared with estimates obtained independently from a numerical hindcast. It was found that generally favourable estimates of the wave spectral properties could be obtained at the site, particularly the mean wave direction and peak spectral period. The study, therefore, provides encouraging support for the use of drillships to acquire valuable metocean data for the offshore industry.