Propeller-less propulsion, foil oscillation, flapping motion

Someone please help me to get this idea out of my mind by explaining why this would not work! I’ve searched the forum and do not see any related posts.

The idea is to create an e-foil without a propeller by implementing other forms of propulsion, like pumping motion or oscillating foils or dragonfly motion. This will remove the drag and danger of the propeller.
One idea is to oscillate rear wing foil (stabilizer) like a dolphin tail. Another idea is to make front wing move like a dragonfly wings. Or create a mast with extension/contraction motion to provide a pumping action (the pitch of the foil can be created by a swivel or soft wing).

Here are some examples;

This will only make sense if your proposed methods of movement are an order of magnitude more efficient than a propeller! Maybe someday there will be other technologies and materials! But so far the Archimedes screw is more effective!

This is the newest technology being used by remote submersibles. Self adjusting Propeller by Hy-Generation - YouTube
Propeller less pitch controlled electric thrusters.

Yah, i think that efficiency isn’t everything that counts - if the mode of propulsion somehow offers a nicer or unique ride then it could still be worth pursuing. Only way to find out is to try it. I’d like to see it done!