Whoever came up with this just went after the carbon buzzword. Ammonia is BAD.
There’s a good reason industries opt for R134a instead of ammonia in industrial cooling applications. Ammonia is fantastic in its physical properties, but dealing with storing ammonia and possible leaks is a nightmare. And that’s in a closed cycle! I can’t imagine the absolute cluster it would be to have that on a moving vessel that needs to be refueled all the time.