Why though make batteries the size weight and shape of shipping containers charge them in ports then the ships can replace empty batteries with charged batterie

Why though make batteries the size weight and shape of shipping containers charge them in ports then the ships can replace empty batteries with charged batteries just like they do containers. I think the world would prefer that over a few thousand nuclear powered ships 1 ship wreck away from making the world sea nuclear contaminated. Which if you understand the water cycle would mean the whole world is nuclear contaminated