Can you swim faster in water or syrup?
The syrup versus water dilemma defeated even Sir Isaac Newton. He reasoned that the syrup being more sticky or viscous than water would slow the swimmer down.
That's quite a natural line of reasoning. Picture how much energy it would take to swim in tar versus water. The geological record gives evidence of just how hard this is in the Le Brea tar flats where the remains of countless struggling animals have been preserved.
Recently an experimenter in the States decided to test Newton's conclusions. The results were surprising.
The answer is more subtle than you first think. Have you ever watched the smoke rising from a lit cigarette. The smoke rises straight up for a few centimeters and then breaks up into swirls and eddies. This is called turbulence. The wing of a jet or the chassis of a speeding Porche create air patterns behind them.
Predicting turbulence is difficult. It's known as a chaos phenomenon. Boeing and Airbus spend millions testing jet bodies in wind tunnels because the turbulence created burns more fuel than moving the jet at 600 miles per hour.
Watch boats as they move through the water. Efficient boats are designed to create as small waves as possible. The wave pattern behind the boat tells you more about how much fuel the boat is burning than the speed of the boat.
Now look at a fish moving through the water. The body is tear shaped and the fins tapers to fine points. The flow of water over the fish is called laminar flow because the shape of a fish's body has evolved over time to create very little turbulence. The flow of water over a fishes body is laminar. The flow of water or syrup over a human's body is turbulent.
There's another fly in the syrup - each fluid has a density. Swimmers do swim faster in salt water than in fresh water. That's because salt water is denser than fresh water. The swimmer doesn't sink as deep in the denser salt water. Since more of his body is out of the water she experiences less resistance and hence is faster. Humans can't swim in air because it's not dense enough. To propel the swimmer forward he needs to have something to push against.
So the question can be refined to, "Can you swim faster in water or a syrup of the same density?"
Back to the experiment. A maple syrup manufacturer kindly offered to donate enough syrup to fill a swimming pool to answer the water versus syrup riddle. No dice - environmental regulations prohibited disposing of the syrup in the municipal drains. An alternative syrup was found with just twice the viscosity of water. The resulting fluid looked oddly like snot. Professional swimmers were enlisted to carry out trials.
The final result - you will swim just as fast in light syrup as in water. The humans shape is so inefficient swimmer that the turbulence created outweighs the effect of the viscosity.