Its some type of river cooter, not sure which subspecies, but you can definitely see a backwards "c" on the third scute (the one towards the rear. Also the yellow plastrom, with some black pattern is also similar. Florida redbellies have a arrow mark on the nose, basically a line running down the head and two lines from the point of the noise outward. This one does not have it.
Its more likely a river cooter than some off the wall hybrid like: river cooter/redbellied/elvis.