Swimming is probably the most nearly perfect form of exercise. It is non-weight bearing and imposes no stress on the bones and joints; it improves cardiovascular conditioning; it is an effective weight-control exercise -- one hour of swimming burns about as many calories as running six miles in one hour; and it is a form of meditation that helps calm the nerves. Swimming also uses most of the major muscle groups, and strengthens both the upper and lower body.

Be aware of the depth of the water and any potential hazards before going in. Know where the pool ladder and steps are. When swimming in the ocean or lakes, watch for rocks, pollution, currents, and sudden changes in water temperature. Never swim alone, regardless of your skill level. Since pool chemicals can irritate and dry the skin, shower immediately after swimming and apply moisturizing lotion.

As you swim, think about a straight line from head to hips to legs. All parts of the stroke are integrally linked. Head position and kick determine how high you ride in the water. The timing of your breathing affects your alignment and also, to some extent, the path of your arms.

Keep your head straight down as you swim; roll your body both ways, even if you only breathe on one side; don't overkick or you will tire out your legs.

Alternate different strokes within the same workout to reduce boredom and work different muscle groups.

Warm up and stretch before swimming hard. A few minutes of stretching before and after swimming will make your stroke smoother and more efficient, and will help relieve muscle soreness.

After warming up and stretching, swim continuously for 10 minutes. Once you can do that comfortably, increase your swim time by 2 minutes every third session. Then add in a set of 10 sprints of about 50 yards each. Rest for about 30 seconds in between sprints.

Do a total-body conditioning program. It is extremely important to strengthen the rotator cuff muscles to keep the shoulder joint tight, so make shoulder-strengthening exercises part of your regular workout routine. Free weights allow you to isolate the rotator cuff muscles better than exercise machines.

Drink plenty of fluids before and after your workout. It's easy to become dehydrated, even during water workouts.