Article from 2009. It is true, large ships burn fuel oil which can be pretty cruddy.
Big ships at sea burn DFM or #1 Diesel. Its ran thru centrifugal purifiers and service filters before its put into the engines because just one of the pistons of one of the engines in a vessel like this costs more than your family made last decade. If it was purchased out of the US it is probly hi in sulfur, but the fuel used to move the worlds ships around the ocean is pristeenly clean.
We had a ship run aground, some years back. Feds burned it in place. It split into two pieces.