This Polyform A3 Buoy makes for a very nice aqua punching bag great for uppercuts. You can buy a Polyform buoy on Amazon: https://amzn.to/2Fqdq7h Make sure to subscribe and turn on the bell so that you don't miss out on new ideas and ways to stay fit and workout at home!
Update: See my DIY channel transformed into a global brand producing the world's first modular cobra bag: https://kewlus.com/