Book excerpt: Fishing vessels can be equipped with energy efficient refrigeration technology applying natural working fluids. Ammonia refrigeration systems have been the first choice, but CO2 units have also become increasingly common in the maritime sector in the last few years. When retrofitting or implementing CO2 refrigeration plants, less space on board is required and such units allow good service and maintenance. Nowadays, cruise ship owners prefer CO2 units for the provision refrigeration plants.Ship owners, responsible for the health and safety of the crew and passengers, must carefully evaluate the usage of flammable low GWP working fluids, due to a high risk that toxic decomposition products are formed, even without the presence of an open flame. Suggestions for further work include a Nordic Technology Hub for global marine refrigeration R&D and development support for key components.