[eisbaw]

Faster: Friction is reduced.

[kokoloko]

Or slower, since you cannot "push" so much water with hands and feet as it "slips" through. Who wins: lower friction or lower viscosity?

[dalke]

These people tested the question experimentally: http://gemini.cems.umn.edu/research/cussler/pool/ . At twice the viscosity there was no noticeable speed difference.

[kemiller]

Typical swimsuit doesn't cover the arms or legs, does it?