It's been proven now that Swimming in syrup is as easy as water:
".. while it might sound like a trivial question, the principle is actually fundamental. Isaac Newton and his contemporary Christiaan Huygens argued the toss over it back in the 17th century while Newton was writing his Principia Mathematica, which sets out many of the laws of physics. Newton thought that an object's speed through a fluid would depend on its viscosity, whereas Huygens thought it would not. In the end, Newton included both versions in his text.
Hamstrung by their lack of access to guar gum or competitive swimmers, Newton's and Huygens' work was mainly theoretical. Cussler's demonstration shows that Huygens was right, at least for human-sized projectiles."
[From today's Good Morning Silicon Valley]