However, a startling fact was discovered by the researchers from the University of Iceland: Guðlaugur’s fat is almost like seal fat. It is more solid and two or three times thicker than human fat.

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/

http://mythbustersresults.com/swimming-in-syrup

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....

http://www.cems.umn.edu/research/cussler/pool/

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.