Answer Wiki. The system would be cued off the pilot's helmet, so it will definitely look where your head is pointing, not your eyes specifically (that would be a gaze-tracking system, which AFAIK hasn't yet been used for this kind of application).
Exercise to Gain Leg Weight. Although you can't make your body gain weight in your legs, you can perform exercises that encourage the growth of leg muscle. Squats, lunges and step-ups are examples of such moves that target the legs and recruit a lot of muscle fibers for growth.
Treading water is tiring at first, which is why it will help to increase the endurance of the leg muscles it uses. There are a few ways to increase leg stamina: Do leg sets: Tread with your hands, then elbows, then entire arms out of the water for specific intervals (probably around 10-20 seconds initially).