This paper explores how design-led and systemic approaches can support sustainability transitions within Waterborne Passenger Mobility (WPM) ecosystems. While current sustainability initiatives in the sector often remain fragmented, technology-oriented, or limited to isolated pilot projects, the research highlights the need for systemic approaches capable of coordinating sustainability efforts across interconnected actors, infrastructures, and lifecycle phases. The study develops three Strategic Directions for Smart Circular WPM ecosystems: Digital Modularity and Flexibility, Integrated Data Management, and Smart Energy Management. Rather than functioning as fixed solutions or technical roadmaps, these Strategic Directions are proposed as enabling structures for system-level change, supporting coordination, adaptability, and long-term sustainability transitions. The paper contributes a transition-oriented and systemic design perspective that moves beyond isolated interventions toward broader strategic configurations capable of connecting projects, stakeholders, and decision-making processes across socio-technical systems. The findings also highlight the role of system mapping and design practice in supporting systemic understanding, coordination, and long-term transformation processes