Context and Motivation: The advent of automated vessels or Maritime Autonomous Surface Ships (MASS) brings new challenges for requirements engineering. In addition to classical, more technical requirements, now a vessel’s behaviour, including its interactions with infrastructure and other traffic participants, has to be taken into account. Relevant requirements can be described in terms of traffic scenarios. Problem: Formal specification of these traffic scenarios provides the basis for clear communication and objective evaluation of behavioural requirements, which is crucial to ensure trustworthiness of MASS. However, there currently is no domain-specific language suitable for this task. Principal Ideas/Results: Initially presented for the automotive domain, Traffic Sequence Charts (TSCs) are a domain-specific visual modelling language for the formal specification of traffic scenarios. In this paper, we present Maritime TSCs, an extension of classical TSCs to the maritime domain, and show that they are suitable for the formal specification of important maritime traffic rules. Contribution: With Maritime TSCs we provide a visual formal language for the specification of maritime traffic scenarios. This language enables clear communication of requirements between stakeholders and automatic, objective evaluation of vessel behaviour.