A lot of us think of cruises as a dream vacation. Unfortunately, cruise ships cause substantial air pollution. Carnival Cruise Lines has been taking corrective action by learning a lesson from the power plant and automobile technologies. Over the next three years, Carnival had a goal of reduce SO2 and trap soot in a filter on up to 32 cruise ships. In addition, while docked in ports, the ships would no longer idle and instead be connected to an electrical grid. This will not be an easy and cheap task but at least Carnival is moving closer towards sustainability.

Source: http://www.foxnews.com/travel/2013/09/06/deal-with-epa-requires-company-to-install-power-plant-technology-on-cruise-ship/