Around 90% of the worldwide trade is carried out through maritime transport making it an economic pillar. However, it is responsible for greenhouse gas emissions as meeting the ships’ energy demand depends mostly on fossil fuels. Therefore, the requirement for an emission-free and sustainable fuel such as hydrogen (H2) is essential. This chapter initially reviews the possible methods to produce, store and use H2 onboard maritime vessels, followed by a case study of H2 production by recovering the waste heat from the propulsion system to power a solid oxide electrolysis (SOEC) through steam Rankine cycle (SRC). Compared to the commonly used energy sources (e.g. solar and wind), taking advantage of the ships’ wasted energy is advantageous for H2 fuel production improving the ship’s efficiency and reducing both costs and fuel consumption. Promising hydrogen storage options are solid storage or through ammonia as an H2 carrier. Finally, H2 can be injected into internal combustion engines as they are commonly used as ships’ propulsion systems. The results show that SRC recovers 3.62 MW of the ships’ waste energy from which 1.42 MW is supplied to SOEC producing 57.179 kg/h of green H2. The SRC and SOEC efficiencies are 21.26% and 69.24%, respectively.