A squat over the top on a BOSU-ball is great for both cardio and your legs. So what you want to do is, you want to place one foot in the middle of the BOSU. You're going to squat down. You're going to jump over and squat again. So when you jump over you're pushing off of your foot. So you push off to lift, you come down, you squat. You push off to lift, you come down, you squat.
Now in order to make this a little bit more intense, you can use weights. So you grab the weights, keep them by your side, squat down. Same squat with your back flat, your neck in line with your back and then you just jump up and go across, jump up and go across. Try not to stay lifted for too long. You want to really get down there and hold it if you can. Stick it for a second, before you jump across and you'll really feel it in your legs. That's how you do a squat and over the top.