When threatened by a predator, these snakes present their tails in such a manner that the tail is exposed while the head is hidden safely beneath the snake's body. The boa squirts a foul smelling liquid from the tail region that would make any predator lose its appetite. Alligators and crocodiles use their tails almost daily, whenever they swim. The flat-ended tail is used to propel the animal through water. Some snakes, such as the sea snakes that spend almost their entire life in the water, also have flattened tails that aid in swimming.
Some crocodilians also use their tails to knock prey off the bank and into the water.
Turtles as a rule do not use their tails for the purposes mentioned for other reptiles. However, having a short, blunt tail, rather than no tail at all, can be vital for a turtle. Adult male turtles generally have longer, stouter tails than females and use their tails to hold onto the female's tail during the mating process. Identifying uses of reptile tails provides insight into some of the ecological purposes to which an appendage can be put. And indeed, although he may not have realized it, this is what the second-grader wanted to know.