Chemical engineers at the University of Minnesota filled a swimming pool with guar gum (which should be familiar to anyone who reads food labels) to answer the age-old question “Can you swim faster in goop than in water?”
High Reynolds number hydrodynamics (roughly speaking, the study of large, fast things in water, where Re>1) is considerably more complex than low Reynolds number hydrodynamics (roughly speaking, the study of small, slow things in goop, where Re<1). Since a swimming human operates in the complicated high Reynolds number regime (at Re ~ 4.5 × 106), there had been controversy about whether people would swim more or less quickly in viscous goop.
Short answer: it makes no difference whatsoever. But lest you feel disappointed, this research did earn Cussler and Gettelfinger one of the highest-profile prizes in the natural sciences: an Ig Nobel! Unfortunately, their goop only increased the swimming pool’s viscosity by a factor of two, which means that all else being equal (and, in fact, all else was equal because their test subjects swam at exactly the same speed as in water) the Reynolds number was only 2× smaller in the goop. This is still very far from the simple yet weird physics that occurs at small Reynolds numbers.
Cautionary note: this experiment is sometimes incorrectly compared to swimming in molasses. This is a dangerously bad analogy. You can swim in a swimming pool filled with guar gum goop, but you cannot swim in molasses. In fact, molasses are very dangerous.