I did try to use a newer edition of a gopro with Bluetooth connection and the gopro app on tablet or mobile. You can record video remotely from the tablet/mobile app and play it back immediately. With the gopro weighted at the bottom at a depth of 1-1.5 m it was working for me. Unfortunately, I didn’t get to refine playing back to the athlete to provide feedback during the session (I little bit rushed during practices). More practice using it away from training to get it right is probably required. This set-up has potential but more experience with it is required to make it viable.