The fifteen largest ships in the world alone emit as many sulfur dioxide per year as 750 million cars, according to a study from the German Nature Conservation Society. Good that there is a chance to end this soon.
In combination with hydrogen - stored in LOHC (liquid organic hydrogen carrier) - even the biggest ships can be turned into electric drive ships.

https://fuelcellsworks.com/news/hyon-as-receives-worlds-first-approval-in-principle-from-dnv-gl-of-module-based-fuel-cell-solution/