This post is dedicated to the use of oxen on and around boats. I am not suggesting that people with boats should go out and get a team of oxen but if you already have a team of oxen, you might consider putting them to good use around your boat.
Oxen used for surf launching and landing
António Fangueiro and lifted from http://indigenousboats.blogspot.com/.
And finally, a vaporware concept for the use of oxen directly on a boat. This one by an unknown Roman writing sometime around 400 AD.
At first glance, it might not be apparent what our Roman conceptualist was proposing, but if you take some time to study the picture you will see that two teams of three oxen are harnessed to two capstans which apparently are linked to paddle wheels at the side of the boat.
The picture comes from a post by Ugo Bardi on the collapse of the Roman Empire. Ugo did not suggest that schemes such as this made the Roman Empire collapse. Rather, he suggested that when the Roman Empire was collapsing, people were proposing to solve the apparent problem with fanciful technology like the oxen in the boat.
Here is an excerpt from Ugo's article:
"The author described all sorts of curious weaponry. One that you can see here is a warship powered by oxen. Of course, a ship like this one would never have worked. Think of how to feed the oxen. And think of how to manage the final results of feeding the oxen. Probably none of the curious weapons invented by our anonymous author would ever have worked. It all reminds me of Jeremy Rifkin and his hydrogen based economy. Rifkin understands what is the problem, but the solutions he proposes, well, are a little like the end result of feeding the oxen; but let me not go into that." And we have to consider transmission losses and the added weight of the oxen, etc. etc.
So, the long and the short of it is that history has shown that it is best to keep the oxen on the beach.