"15 largest ships in the world emit as much nitrogen oxide and sulphur oxide as the world’s 760 million cars."

First step is countries ban the vessels from coming anywhere near land. I guess that keeps pollution out of sight, out of mind. Next step.... I don't know. But I'm hopeful soon enough the powerplant will be significantly greener. In the short term you can get 1 order of magnitude from regulation. In the long term it's new technology.