With the advent of assistance systems that classify into the four degrees of IMO maritime autonomous surface ships comes the challenge how to verify and certify such systems, which, in many cases, rely on AI-components for perception or recommendations. One approach to verification and validation of such systems proposes to define test cases as traffic scenarios, i.e., evolutions over time of traffic situations. A necessary prerequisite to apply scenario-based approaches is the correct conduction of specified tests. Especially in physical tests, to ensure correct conduction, the specification has to be communicated clearly to the person conducting the test and the executed test has to be checked against the specification. An appropriate (intuitive and formal) specification of the scenarios to be recreated in testing can provide these clear instructions and an objective criterion to assess correct test conduction. In this work, we report from a case-study with a graphical scenario specification formalism (as originally defined for the automotive domain and recently extended for maritime scenarios) following the question whether we can formalise relevant situations and scenarios from real test campaigns using this formalism and see how understandable the results are for maritime practitioners not trained in formal methods.