

A fan on a boat would work. There are these fan boats people ride through the Everglades. There are propeller sea planes. The difference to a sailboat is the profile of the vessel under water. A sea plane has two or three smaller areas that are submerged. The everglade ones are just breaking the surface of the water and are very flat so they can glide over water and plants. A sailboat has a big, often deep profile under water, the whole length of the boat, possibly a keel underneath. And that’s moving through water, which is thicker than air. So you need possibly more than one propeller and the engine may need to give you more horsepower to move the boat through water with the force of the air above deck. That’s inefficient so boats tend to move their propellers under water.
A few container ships have a spinnaker sail they can deploy. If the wind is favourable they can reduce the engine output and save diesel. Just in case you’re wondering about the reverse situation.






These systems vary by country and you’ll find fault with most of them. They are more often than not rating systems that were introduced to appease a loud group in society, possibly the pious folks were one of those. Society’s natural inclination “to think of the children!” makes these rating systems more about age appropriateness than about clearly labelled content. I can see the logic in your approach to the subject. Logic probably wasn’t the driving force behind introducing labels such as “parental guidance” or “restricted.”
I think it might be easier as a committee to be compelled to come up with an age of people, for whom the content is appropriate, and not argue over labels until they’re blue in the face. Is vaping drug use? How much blood (if any) is required to be labelled violent? Etc. Can this committee agree with a majority vote that 12 year olds probably shouldn’t see this? That’s probably easier.