Wearable Augmented Reality Displays (WARDs) present situated, real-time information visually, providing immediate access to information to support decision making. The impacts of WARD use on operator performance, Situation Awareness (SA), and communication in one safety-critical system, marine transportation, were examined in a real-time physical simulator. WARD use improved operator trackkeeping performance, the practice of good seamanship, and SA, although operator responsiveness decreased. WARD users who used more closed-loop communication and information sharing showed improved threat avoidance, suggesting that operators can avoid accidents and failure through WARD use that promotes sharing and confirming information. WARD use also promoted information source diversity, a means of developing requisite variety. These operational impacts are important in safety-critical settings where failures can be catastrophic.