Water exercise can help you improve your cardiovascular fitness and increase your strength and flexibility, according to the Centers for Disease Control and Prevention, or CDC. It's also the perfect medium for individuals with exercise contraindications, such as obesity, rheumatoid arthritis or other chronic illnesses, which make land-based, high-impact exercise more difficult. You don't have to limit yourself when you perform water exercise, so go ahead and target any muscle group you want, including your hips and abs.
Stand in water at least waist deep with your back to the pool's wall, your hands resting on the deck for support. Lift your right leg out to the side as high as you can lift it, then swing it down and through the water, crossing it in front of your left leg as far as you comfortably can. Swing it back up and to the right again, continuing the movement for 15 to 20 repetitions before switching sides. This will target your hips and inner thighs -- you can tie a water noodle around the ankle of your swinging leg to increase the resistance of the exercise.
Stand in water shallower than waist-deep, starting on one side of the pool so that you can move across the pool's width. Bend your knees and your elbows, crouching in an athletic stance. Step laterally with the leg farthest from the pool's wall, pressing against the water's resistance, then bring your other leg to meet it in the center. Step laterally again with your first leg and continue this side shuffle across the pool. When you reach the other side, return across the pool, starting the movement with your opposite leg. This exercise will work your legs and hips, according to water aerobics instructor Kathi Kense in Stayton, Oregon.
Stand in waist-deep water while facing the side of the pool. Lean back into a float and lift your legs, placing them on the pool's deck so that your calves lie flat on the deck. Cross your arms over your chest, tighten your abs, and hinge at your knees and hips so that your butt drops down into the water while your chest remains at the surface of the water, your body forming a "V" shape. Keeping your abs tight, pull your torso toward your knees as though performing a sit-up. Release the movement and hinge your torso backward into the "V" shape. Perform 10 to 20 repetitions.
"Fitness" magazine uses the wave maker exercise as an option for toning the abs and butt. Stand next to the side of the pool, facing the wall in chest-deep water. Hold onto the pool deck with one hand and place the palm of your opposite hand on the side of the pool, under the water with your fingers pointing down. Extend your legs behind you as though you're trying to float on your belly. Draw your knees and ankles together and begin performing a butterfly kick, moving your legs in unison. Initiate the movement with your abs and hips by forcefully pushing down into the water, then transferring the movement to your knees and ankles. Continue kicking with as much force and speed as you can for 30 seconds. Rest, then perform the exercise two more times.