I don't disagree that nuclear propulsion has a long way to go before becoming safe enough for civilian use and might require extra security and regulation forever, but we need to do something other than dumping bunker fuel waste into the sea and atmosphere even coubting in several terrorist attacks and accidents it might still end up killing less people using nuclear. As you say going with hydrogen and by extension ammonia, which is probably the only viable way to fuel ships, will require unthinkable amounts of renewables which is mostly intermittent energy meaning hydrogen electrolysis plants will have to be ramped up and down as the wind blows or the sun shines. this makes the efficiency calculations even worse for an already super wasteful undertaking. i guess we could potentially use nuclear but why waste 80-90% of the energy created by converting and then using hydrogen ? My opinion is that we need to throw much more money at making nuclear fission safer.