: Ice floats so density decreases as water gets colder. Viscosity most likely
: would decrease also.
Ice floats because of the way the molecules come together to form a solid, but cold water is denser than hot water, but only by a very little.

I wonder about viscosity, I think it could go either way, but probably decrease, or maybe not change at all.

I think the more important questions might be how the temperature affects how much debris there is in the water and how it might soften your varnish, making it more liikely to be scratched.

On that subject, the condition of your varnish probably makes a difference.

And the air temperature might change the winds, which would affect your paddling speed.

And what about solar winds? During any given time of day a lower temperature might make it easier for them to hit you and your boat, speeding you up or slowing you down.

See what I'm getting at?

I just couldn't resist.