Swimming need not just be a cardiovascular workout. Mixing up your routine with these aqua aerobic exercises is a great way to strength train as the resistance added by the water loads up the muscles without having to resort to a gym or strength training equipment.
Arm dips (for chest, back muscles, triceps)
Hop as high you can at pool's edge. Lower body slowly with elbows at sides.
When elbows are bent at 900, lift yourself again without touching pool's bottom.
Front scissors (for upper leg and abs)
Raise legs as far apart as you can with back to the pool wall. Cross your legs, spread legs wide and then cross right over left.
Extend arms to sides; pull them down past the thighs and cross them as far as comfortable. Sweep them back to starting position on same path.
Stand with your back against pool wall and hold it with both arms. Lift legs straight to water's surface. Cross feet over and under each other. Alternate with both legs. Let your leg and stomach muscles do the work.
Leg lifts (for abdominals)
Sit with your legs straight in the water. Support yourself with your hands and lean back slightly. Lift legs up together with the toes pointed and hold. Lower legs and start again.