SEASTARS main objective is to demonstrate a well-to-wake GHG emissions reduction of minimum 30% by 2030 (compared to 2008) as well as a 20% energy efficiency improvement (compared to 2022 reference performance) on eight market-ready vessel designs (4 retrofits and 4 newbuilds) addressing inland, short and high-seas shipping by combining different emission reduction and efficiency improvement technologies that will be market ready by the end of the EU project. SEASTARS will help shipowners not only to evaluate the vessels emission reduction and efficiency enhancement but also to generate appropriate action-time plans for the decarbonization process and to quantify the related investment decisions, so to adapt their fleet to be always in line with the imposed regulation. Emission reduction and efficiency improvement technologies are designed as modules that can be added, scaled up or replaced in phases over time into a ship that is designed in a flexible and traceable way, enabling decreasing emissions progressively while maintaining a reasonable investment risk, controlled by the shipowners.