Shark skin may be de rigueur poolside at the 2012 Summer Olympics. A new study finds that microscopic scales known as denticles propel the predators through the water  at speeds 12% faster than they would otherwise achieve without them. To fish out how this happens, researchers mounted pieces of shortfin maco (Isurus oxyrinchus) and porbeagle shark (Lamna nasus) skin on flexible robotic fins and placed them in a tank. By analyzing water flow over the skin, the team found that denticles determined the proximity of swirls of water, called vortices (visible in the video), to the fin. Intact denticles produced swirls close to the skin, the researchers report in The Journal of Experimental Biology, creating low pressure areas that pulled the fin forward. Fins with their denticles sanded off produced vortices further away from the skin, reducing fin flapping speeds. The scientists note that manufacturers of Olympic-worthy swimwear, designed with dimples to reduce drag, may want to build in little ridges instead.
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