Despite the adoption of crew resource management training for bridge teams over the last decades, the training is still heavily focussed on technical achievements. In an educational context, the situation is more problematical, since with requirement of developing the technical skills, there is a need to build and evaluate the non-technical skills of cadets with little experience in bridge team management. In parallel with the application of team leadership models, the Portuguese Naval Academy conducted a research to improve the development and assessment of non-technical skills in bridge simulators. This paper describes the method used to identify the key non-technical skills required for naval cadets and to develop a behavioural marker system for their measurement. A literature review of behavioural marker systems was supplemented with an analysis of interviews conducted with students and simulator instructors. Additionally, further analysis of Portuguese Navy accidents reports was made, applying the HFACS framework to identify the relevant nontechnical skills involved in the accidents. The resulting rating system covers five skill categories (leadership, situational awareness, communication, team work and decision making), each one with three rating elements. The framework is currently under evaluation tests in bridge simulators sessions, within an educational context.