Abstract: The present invention provides a hydrogen powered, modular, SWATH vessel (1); the vessel (1) comprising a plurality of modular vessel components (3) including: a plurality of lower hulls (11, 12) for containing one or more hydrogen storage tanks (100); a plurality of struts (20) each reversibly connected to one of said lower hulls (11, 12); a fore cross-structure (50) and an aft cross-structure (60) each reversibly connected to a strut (20) connected to the first lower hull (11) and a strut (20) connected to the second lower hull (12); and a deck structure (90) reversibly connected between the fore cross-structure (50) and the aft cross-structure (60).