GreenHopper is the first Danish zero-emission ferry developed as a test platform for autonomous waterborne navigation technologies. This paper presents the technology development within the innovation project ShippingLab Autonomy, which led to the commissioning of GreenHopper at Limfjorden, Denmark, in December 2022. The research resulted in a holistic system architecture for surface vessel autonomy, based on the distribution of functionality and responsibility across software modules, akin to the structure observed in the International Maritime Organization (IMO) Seafarers Training Certification and Watch-keeping (STCW) regulatory framework. This approach supports safe behaviors of individual modules and autonomous navigation at the system level. The paper details the individual modules, their specific features, and benefits, and highlights elements of the regulatory framework to facilitate technology approval by maritime authorities. Lessons learned and continued technology validation in dedicated operational scenarios are also discussed.