<p>In this study, we explore the current practices of experienced instructors in developing scenarios for maritime simulator training and assessment. Scenario design is fundamental to effective simulator-based training but remains underexplored in extant literature. Through a series of semi-structured interviews (<i>n</i> = 16), we identify the core concerns of instructors designing scenarios; (1) realism, authenticity, and fidelity; (2) designing for students’ requirements; (3) the importance of clear learning objectives. Based on the results, we propose that <i>functional congruence</i> is a more fitting term than realism, authenticity, and fidelity in this context, as effective simulator training requires a balance between a simulator realistic enough for immersive learning experiences, and a focus on clear learning objectives. In consideration of the need to train students to function as part of a team of competent experts, moreover, we propose the introduction of an established instructional design model into the scenario design process. The proposed model has proven successful in simulator-based training in the similarly high-risk and safety-critical field of healthcare and has the potential to both complement the current practices of experienced instructors and act as a valuable resource for those newer to the role in designing training transferrable to professional practice.</p>