Exactly - you need to decouple efficiency of mode, from amount of transport done in that mode if you want to make sensible decisions about which mode is best.

Or put it another way - if all that cargo going by sea went by air C02 emissions would be 100x more.

Obviously saying sea travel is massively more efficient doesn't obviate the need to reduce that as well.

but once you put people on it you f that number up.