“The dorsal shell of the green turtle, or carapace, is wide, smooth, and brownish-olive in color. The underside of the shell, or plastron, is yellow. Green sea turtles are so named for the greenish hue of their skin. They have heads that cannot retract into their bodies, a trait commonly associated with turtles. Reaching speeds of up to 56 km/h (35 mph), their streamlined shell and paddle-like flippers aid in their ability to swim quickly and with grace.”
The main benefit of wearing a shell is that is helps protect turtles from predators. Made from bone covered by hard plates called scutes, the shell makes it difficult for many predators, such as raccoons and otters, to get a bite of tasty turtle meat. Many land turtles can draw their legs, tail and head into their shells, leaving only a hard, oddly shaped shell in reach of predators.
Turtles sport different shell shapes depending on their preferred habitat and other defenses. Some large land turtles, called tortoises, move too slowly to avoid predators, so their only protection is their shells. These shells tend to have a domed top section, called the carapace. The rounded shape makes it harder for predators to get a good grip or mouth hold, allowing the turtles to hide in their shells and wait for the predator to give up. Sea turtles, on the other hand, have shallower, more streamlined shells to help them swim faster through the water.