You can do leg lunges to help tone your legs in water aerobics. I usually do these lunges to warm up, for about 30 seconds to a minute. Then halfway through your routine or even at the end you can do regular lunges, forward and back. When you do lunges forward, you want to make sure that your knee is directly over your foot, and then you're going to step, and then we can go backwards. Usually I have participants do leg lunges all the way to one side of the shallow end to the another, and then I have them go backwards. They'll do the length of the shallow end about two to three times depending on their level. And that's a great workout for your quads, your hamstrings, your inner and outer thighs and your calves.