Shortfin mako sharks are the cheetahs of the open ocean, with some estimates putting their top speeds at more than 100 km/hr. That swiftness may be the result of more than just powerful muscles and a streamlined shape. All sharks have enamel-coated scales, known as dermal denticles, that resemble tiny, translucent teeth, and on fast swimmers like the mako the scales are small—about 0.2 mm, as shown in figure 1. Not only do those scales act as a suit of armor, they also reduce the shark’s hydrodynamic drag.