> Is nuclear propulsion for ships a viable option?

Yes. There are half a dozen countries with mature viable nuclear naval propulsion technology, another half dozen in development. Hundreds of vessels already built.

The fuel cell technology is several decades away from being available to power ships, and we don't have decades to decarbonize the economy. The Arctic ocean is gonna be totally melted for the first time in human history in about a decade or so, and from there on the feedback loops are gonna make the race against global warming even more hopeless than it already is.

Go nuclear.