We need a multi emoji I wanted to laugh but at the same time this is sage advise. I gave it a like. but here is the laugh for the comedic delivery.To answer your question one can probably be kept "ILLEGALLY" in a pool depending on what type of turtle it is. Some eat jellyfish, some sponges and some living things.
Either way it will not fare well when you are in jail, but if that doesn't concern you, find out what that specific turtle eats in the wild.......Then turn yourself in to the Dept of Environmental Protection.
While you are in jail, the "turtle" authorities will release the turtle back into the sea and maybe send you post cards of it's travels.
Many years ago, they used to sell baby sea turtles in a large store in Manhattan. (Aquarium Stock Company) They sold for $50.00. Now those people can't use their bath tub because there is a 400 pound turtle in it.