Actually I record my team during swim sets and discuss mistakes I see as part of the warm-up next session. I’m using a cheap gopro clone for the recording which provides underwater footage in HD quality.
I can’t provide immediate feedback to the team with this solution though so I wonder if someone has already experience with real-time monitoring?
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.