Growlers in otherwise open water present a distinct risk to vessels, particularly when waves are present. Waves can hide “small” pieces of hard glacial ice while causing impacts with them to be more intense, or to occur at locations above a ship’s ice belt. To explore this risk, we developed a novel time-domain simulation methodology that combines the wave-induced motions of the ship and of a growler to predict impact locations and intensities. A combination of linear and nonlinear methods captures the relevant physics efficiently. When repeated for several thousand growler encounters, this enables the impact probability to be mapped onto the hull. Vulnerable areas of the hull are identified by showing only impacts that are hard enough to exceed the local structural capability. Operational guidance to mitigate the risks is obtained by repeating this at different speeds and headings. Applying both mitigations in combination improves the ability to design and safely operate vessels in polar waters where growlers may be present in demanding sea conditions.