FLEETfor55 is an ambitious project to align the European waterborne sector with the EU's "Fit for 55" environmental targets for 2030. This will be done through a holistic roadmap that identifies the most cost effective and sustainable implementation of Energy Efficiency Technologies (EETs) onboard short sea, inland waterway and high seas vessels. To achieve this, FLEETfor55 will evaluate EETs paired with new vessel designs and retrofits – collectively defined as use cases. Six retrofit use cases and four new vessel design use cases, each employing a "design-for-operation" approach will be optimised for both energy use and environmental compliance throughout each use case’s lifetime and for different operational scenarios. Additionally, the project will integrate a decision support system into a web-based digital platform to rapidly assess and benchmark use cases, achieving quantifiable energy efficiency savings and reduced emissions. This system assesses use cases with the help of key performance indicators that align with the EU’s 'Fit for 55' legislative package and the International Maritime Organization’s indices such as CII/DCS, EEXI, and EEDI. Key strategies include developing detailed business models for each use case to ensure market adoption, and the establishment of the Technologies Innovation Network. The latter will ensure that EETs are effectively matched with end users, promoting the adoption and practical implementation of new technologies in the waterborne transportation sector. These initiatives position FLEETfor55 not only meet stringent EU environmental standards but also to set a new benchmark for future environmental excellence in waterborne transportation.