[CWuestefeld]

I don't think so. I think that at the extreme (say, the consistency of peanut butter), the amount of force you expend simply in inserting and extracting your arms (that is, not in the direction that propels you forward) becomes excessive.

[sliverstorm]

Or, to put it in terms of a simple thought experiment-

can you 'coast' or 'glide' in water?

can you do the same in molasses? How about caramel?