I'm specializing on "green" wind assisted cargo ships.
wind assisted huh? I invented an eco-friendly engine where water is piped in via manholes beneath the waterline. water is then filtered and used to power a hydraulic engine. Water vapor and steam is the exhaust, so it can form clouds, which would rain down more water to replenish the ocean.
the idea was originally used to clean the Yangtze River, but I guess it could apply anywhere. And the ships that are equipped with the engines are bullet-shaped to reduce wind resistance, making it go fast, but not use too much water.