I don't know much about them, but I have seen them (3-Stripes) around here. I actually caught one in a nearby lake. They are so 'cute' xD. I assumed they would stay small and I wanted to keep it, but I had no idea how many gallons of water it needed to be kept in.
They do seem to spend a majority of their time underwater from what I have seen. I rarely see them basking, but I see the yellow bellies and RES basking very often. My friends and I actually spotted two of them mating underwater once xD.