The Mythbusters checked the increased viscosity myth (opposite presumption, same speed is possible) and found it plausible.
Re:The truth about cold water
by alex_stoddard on Friday July 09, 2010 @12:51PM
(#1501251)
It has been a long running debate which way viscosity would affect swimming. Higher velocity increases resistance to forward motion but also allows for more propulsive force from the swimmer - which will dominate?
It turns a research group at UMN actually was crazy enough to do the test - it looks like the effects balance for a human swimmer.
http://it.umn.edu/news/inventing/2004_Winter/goingforthegoo....
Re:The truth about cold water
by SkyMarshal on Friday July 09, 2010 @03:22PM
(#1501875)
As as a swimmer, I know I'd much rather swim in cold water than warm, at least as far as pools go.
It's easier to maintain momentum and glide in cold water, whereas swimming in warm water feels like you're swimming in molasses.
Also, as my body heats up, cold water feels more cooling, obviously.
This is very size and speed dependent, but increased viscosity delays separation and can actually reduce drag [1], [2]. In any case, the viscosity difference is not huge and water temperature is normally not precisely controlled for swimming events.
"Most people [...] suffer from vasodilation in extreme cold."
Only when the core is doing well [3], the opposite (vasoconstriction) occurs otherwise.
[1] http://jeb.biologists.org/cgi/content/abstract/204/1/81
[2] http://www3.interscience.wiley.com/journal/120798746/abstrac...
[3] http://www.springerlink.com/content/l776704k04017q43/