Looking at the image it would be super cool if it could be used as a tail, of course I see now it would require different phenotypes for each boat model so pc wouldnt stand like idiot in middle but would be directing boat at ruddle or sitting somewhere.
Problem is the ammount of work needed to be done for this is overwhelming, Im surely not capable of doing this in my currently limited time frame.
Here's a mock up in the toolset of the most favourable case:
Here I've superimposed the riding phenotype on the walkable water tile and the smallest boat creature.
For use as a tail, the boat model would need a slight position adjustment to sit forward of the humanoid.
The same could be done for other small boat models which I haven't converted to creatures.
I'm not sure it looks good enough, though.
P.S. In making this, I discovered that horse-and-rider look pretty good wading through the walkable water. By design, dismounted humans are barely visible (water above their eyes) unless using the flying/swimming pheno.