Swimming is an excellent exercise that incorporates multiple muscle groups, is generally easily accessible, and is most importantly ... fun! Swimming offers both cardiovascular and strength benefits, as movement through water is 12 times more resistive than movement through air. Swimming is a total body exercise that strengthens the core, shoulders, arms, hips and legs in one easy exercise. Swimming is also a great low-impact exercise for the active population with physical impairments, such as arthritis and other musculoskelatal complications.
Before getting wet, make sure you know the basics. If you are new to the water, take a swimming class. This is to ensure proper saftey in the water and also allows one to get the most out of their excercise by utilizing proper form. Once you're comfortable, begin in the controlled enviornment of a pool, covered by a lifeguard for saftey. Once you have mastered swimming laps in the calm pool enviornment, it's time to take your exercise into the great outdoors. Advancing to lakes -- and eventually the ocean and surf -- will add a level of difficulty to your exercise by introducing currents and waves. Only progress to these levels if you are a competent swimmer and under the watchful eye of a lifeguard.
Swimming is the perfect exercise in the summer. Not only do you get a full body workout, you also get to enjoy the nice weather. As with all exercise, make sure you are medically cleared by a doctor beforehand, and always properly stretch and warm-up to reduce the chance of injury.