PROPULSION DEVICE, design and shape.

Yes, propulsion device looks primitive, more if we take a look to the work in this matter the last hundred years. So, something is going wrong, the sea waves are plenty of power and is necessary to know how to use it, but the way of development of this technology is looking for an horizontal fin, like dolphins tails. However, a vertical fin, like a shark tail, increases estability, reduces drag and almost all the motion is used to propel the boat. Then, we will take a look at the nurse shark and yuloh.
The dolphin's tail is too efficient, but this one swimms in different way than a boat navigating. I can't imagine my boat jumping over the waves. Sharks or tunas swimming more like a boat navigate.