The ocean shipping industry is under pressure to reduce emissions from their ships fueled with heavy diesel fuel. Methanol, ammonia, maybe hydrogen are possible alternatives.
Article points out that the US Navy has nuclear powered ships and submarines with a good safety record. Could nuclear work for merchant ships?
The US operated the NS Savannah from 1962 until 1972.
I might be biased, but the Savannah was the prettiest cargo ship I have seen (unfortunately, only in pictures).
Russia has also operated nuclear powered merchent ships. Presently, they have a fleet of nuclear powered ice breakers in the Arctic, which are used to keep the sea lanes open for the northern passage between Europe and Asia.