Sea turtles are marine reptiles with streamlined bodies and large paddle-like flippers that make them well adapted to life in the ocean. Unlike land turtles, they cannot pull their heads and flippers into their shells; their rear flippers act as rudders for steering while they swim.
Species also show feeding adaptations—for example, hawksbills use sharp beaks to pry sponges from reefs, loggerheads have crushing jaws for hard-shelled prey, and leatherbacks can dive nearly 4,000 feet and trap jellyfish with spiny mouth papillae. Adult females still return to land to nest, often after migrating hundreds to thousands of miles between feeding and nesting areas.
Source: NOAA Fisheries — Sea Turtles