Some turtles, but not all, are herbivores. Turtles may all be anatomically similar, but they live in very different environments depending on species. Some turtles live in freshwater streams, while others live in the open ocean or entirely on land, placing them in very different dietary niches.
The green sea turtle, Chelonia mydas, is a pure herbivore, but most sea turtles are predators. Several species specialize in a particular kind of prey: leatherbacks feast on jellyfish, while loggerheads crack open the shells of crustaceans with their impressive beaks. Other sea turtles are omnivores, eating whatever comes their way. Semi-aquatic turtles tend to be omnivores though many are carnivores as hatchlings. The tortoises, which are land-dwelling creatures, are almost entirely herbivores. Some species, mostly those living in the tropics, scavenge carrion as they find it but do not seek it.