Augmented Reality (AR) technology has been widely investigated to support various navigation tasks, including initial approaches that suggest its potential use on ships. For maritime navigation, skippers use a variety of information displayed on a ship’s bridge. However, the constant shift of focus between this information and the outside view of the ship might pose cognitive as well as safety challenges. Here, AR could facilitate the navigation of ships by overlaying the real-world view with spatially anchored visual navigation aids. Despite this potential, previous work mainly presents conceptual approaches, technical tests, or user studies performed in ship simulators only.In this paper, we evaluate an AR-based assistance system in the actual real-world water environment, where technical issues and varying physical conditions could influence the system’s usability. In collaboration with hydrographic experts following a user-centered design approach, a functional AR system was developed that virtually displays navigation aids on the water surface. In a field study, ten skippers used the system to navigate a ship along a path through a port area. We assessed the accuracy, perceived workload, and user experience of participants. In addition, qualitative feedback was thematically analyzed to retrieve insights about the skippers’ attitude regarding using AR on actual ships. We report lessons learned about aspects such as ergonomics, perceived safety challenges, as well as envisioned further use cases and extended data integration.