The CO2 footprint for cruise ship passengers is eight times that of land-based vacationers.
Most cruise ships burn low grade bunker fuel laden with sulfur oxides, heavy metals, and other toxicants. Pollutants from exhaust emissions are removed by ship scrubbers spraying seawater into smokestacks and returning the acidic wash water laden with heavy metals etc. back into the environment, turning air pollution into a water pollution problem.
Over 120 ports world-wide have banned cruise ships from dumping toxic scrubber waste.