Global shipping is probably not talked about much because it is extremely tough to push any standards. It took forever to get an agreement to stop using the horribly toxic sludge they used to use in international waters. You are right though. It is 100% something that needs to be focused on and fuel cells would help a fuckton in that area. Sure they are not as energy efficient as BEVs but they are a ton better than the garbage fuel cargo ships currently use.