When rowing, 3 works are performed: 1) pushing the water back 2) carrying the oars 3) pushing the boat forward. Maybe somehow it will be possible to come up with another principle – to limit ourselves only to pushing the boat forward in order to spend less effort? I understand that a fulcrum is needed, and a lever, and the transfer of the paddle and pushing the water play this role, but still, suddenly it is possible in an energy sense to perform these functions cheaper or to do without them at all? The same applies to aircraft.
In a jet engine they figured out how to avoid the transfer of the paddle :) But the air is still being pushed back... This is a lot of work, needed only to push the vehicle forward. Maybe it is possible to do it somehow without pushing water and air back?
On hard surfaces, it is possible to save this energy significantly better. For example, jumpers – kinetic energy goes back and forth, and is not absorbed by the environment, due to this it is possible to increase the running speed to 40 km / h or reduce energy consumption at the same speed. Wheels on the ground allow you to move much faster than propellers on the water. Perhaps there is a way to somehow give liquid and gaseous media the properties of solid ones for a while, at the moment you are pushing from them? Maybe this will solve the problem?
I'm not an expert in physics, but it seems like when hitting water, it has the property of a solid body for a short period of time? Maybe then a much faster blow is needed – so fast that the water will behave like a solid body? Or come up with something else. It may be inconvenient to use a magnetic field, because an external environment with an intense magnetic field is needed. But maybe something will still be able to come up with?