In order to safely operate sailboats, captains often rely on proper interpretation of several marine aspects to make decisions. In this project, we have developed an Augmented Reality System (ARS) to provide captains of sailboats with a centralized sensor data server and a visualization method. We have deployed an experimental proof-of-concept version of this system on our research vessel, SV Moon shadow. Assistance in navigation is of particular interest for small sailing vessels as they are sometimes sailed by the captain alone. At the same time there are a large number of data inputs such as wind, tide, weather, position, and presence of obstacles such as logs or kelp that have to be considered to choose the proper course of action. We introduce a visualization tool that provides an interface for representing a wide spectrum of relevant marine data. The interface relies on a real-time data server that provides information about the status of the vessel (wind, GPS, gyro, accelerometer, depth sounder etc.) An important component of the interface is a debris detector that analyzes data from a camera mounted on the bow in order to warn a captain about a potential collision. We have also examined initial feedback on this tool from a number of users.