Jumping jacks is a really easy cardio exercise that you can do in the water. What you do is just a regular jumping jack that you would do on land. You can use weights just to make it a little harder or you can go in the deep end. Now with weights it looks like this. You can use it without weights, it's a little easier. If you are in shallow water you want to make sure you keep your hands in the water. You don't want to lift them out of the water. Make sure you don't go to high with your arms. Okay. And like I said before in deeper water it's a little harder and with weights it's a little harder. There's all different kinds of weights that you can use. There's light ones, there's medium weights, and there's heavy weights. So just get the weights you're most comfortable using, and you can do jumping jacks, and get a really good cardio workout. If you want to make your jumping jacks even harder than it is using weights, you can power jacks, which is an alternative method of jumping jacks. And that is how you do jumping jacks in water aerobics cardio workout. It's very easy to do.