If you consider than frictional resistance increases at an approximately exponential rate as velocity increases, minimizing the drag due to surface finish is important to minimizing the effort required to paddle a kayak at any given speed (where wave drag is not coming into play). The only link I have at hand specifically dealing with kayak surface finish is by John Winters (see below); he notes that typical wear and tear of a hull's surface could easily double the coefficient of friction over a single season, which is not a trivial increase, since the increase in the coefficient of friction will give you a linear increase in drag for a given velocity.

So, 50% increase in the coefficient of friction due to a rougher hull surface will cause a 50% increase in effort to maintain the same speed you were capable of before the surface was damaged.

As for creating a shark-skin like hull surface, there have been at least a couple of threads on it here and at QajaqUSA. Bottom line was, IIRC, that at the speeds paddled by most recreational kayakers, the effect will not likely be noticeable. Creating the surface, much less trying to maintain it, would by most all accounts, be a very costly and time consuming endeavor.

: I imagine it would be difficult to reproduce sharklike denticles with the ROS
: but was wondering if anybody out there had any insights into the effects
: of surface finish on drag reduction?

: more of an academic question really as I am a mid field plonker so this type
: of fine tuned performance enhancement would be lost on me plus I like
: shint wood.
: Cheers, Craig