Do ya think that's what makes this stupid? Well, consider the fact that a single ship polutes the atmosphere with more carbon in a day than all the cars in the United States in a year... then reassess this idea.
Oh come on. That statement doesn't stand up to the slightest snifftest.
There are 250M cars in the US which means that you would need to have 365x250M (91 billion!) cars for them to emit as much carbon in one day as one of your ships supposedly does.
Yet road transport still emits 5-6x as much as maritime transport:
How many cars, buses and trucks would there need to be to emit 5-6x as much carbon as the 10s of thousands of ships there are worldwide?
I suspect you could be maybe 6 orders of magnitude out there.
OK maybe you misapplied some other pollutant? Sulphur Dioxide maybe? Ships burn very dirty bunker oil after all. Here's an article that reckons the largest of container ships can produce the same amount of SO2 as 50M cars in the same timeframe.
Now you're down to only 3 orders of magnitude (5 x 365) out - eg 50M is only a fifth of the number of cars in the US and correcting for one day vs one year.