The idea is simple: to propulse a boat we need an oar and a boat, applying force to the oar we have the motion. But, what happen if the force is applied to the boat by the waves? Lots of smart people still working in develop fins, doing equations, investing money and time, having masters and titles..............Don't be smart, just modest and humble is much better to learn and found solutions. I have a tender boat, and a sculling oar astern, that's it.