Tortoises or Turtles?

Green tortoises aren't really tortoises; or so I've been told. They are really turtles; just like the black creature which shared my childhood home ; the Asian box turtle which I mistakenly identified and promoted as a tortoise. Now, if you have any doubts, let's just consider this: A tortoise lives on land and doesn't swim. It crawls on its elephant-like feet while a turtle which can live both on land and water, swims like a fish with its flipper-like feet. Next time when I see Leonardo, Donatello, Michelangelo and Raphael, I'll check on them to see if they have feet like elephants or flippers. For all I know , TMNT or Teenage Mutant Ninja Turtles may not be turtles but tortoises.