The workout: There are four basic strokes: butterfly, backstroke, breaststroke, and freestyle. Most recreational swimmers stick with freestyle also known as the crawl. You can either swim laps in the pool or head for an ocean, lake, or any other body of water that's large enough and deep enough to submerge your body.

upside: Water's natural buoyancy. It supports about 90 percent of your body weight, so there's no painful jarring of your joints. Not only does this prevent injury, it helps prevent post-workout soreness. Water is also 14 times thicker than air so it offers plenty of muscle toning resistance in any direction you move.

downside: You need a certain amount of skill so you don't, well, flop around like a fish out of water. Scientists speculate that you burn less fat and more glucose and that water keeps your body temperature and heart rate somewhat lower than do land-based workouts. For this reason, swimming is not the best choice for weight loss.

• Supplement your swim program with 2-3 weekly weight training sessions to ensure that you stimulate bone growth.

• If you haven't dipped a toe into a pool since summer camp, take a lesson or two. Breathing rhythm and technique are the key to flying through the water like a dolphin.

requirements: Gear: A swimsuit and goggles. For skill drills you may want to have a kick board, swim fins, and hand paddles on hand.
Instruction/Facilities: A pool or some other body of water.
Time: 20-60 minutes, 3-5 days a week.

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