Health and fitness expert Jane Katz's summary of body benefits from swimming:

Heart, blood vessels and lungs: "An excellent aerobic (heart-pumping) exercise." When done systematically, lungs increase "in size, capacity and efficiency." The heart "becomes more powerful, more fit." Blood vessels "increase in number, and they may even become more flexible."

Muscles: "The single best exercise for toning your arms, shoulders, waistline, hips and legs all at once."

Flexibility: "Long, sinuous motions . . . actually elongate your muscles while strengthening them."

Sans side-effects: "The average swimmer has virtually no injuries to worry about." Sports medicine specialists "unfailingly recommend" pool time "to those who have sustained injuries in other sports, or in life."

Weight loss: It burns up from 300 to 800 calories per hour, depending on your stroke and speed (300 to 500 for sidestroke, breaststroke or backstroke; 800 for butterfly or crawl). Also, "strenuous exercise actually helps to curb your appetite."

Anti-aging: "Lack of exercise is the most important factor in premature aging." Swimming is an exercise that "can continue to help slow the aging process for as long as you live."

No overheating: "The water acts as a natural coolant for your body." Katz notes that swimmers sweat, though "you may not realize it." Since the air near the water surface is freer of pollutants, a foreward to her book claims some young asthma sufferers may compete in swimming when they can't in other sports.

Therapy: "The water's buoyancy supports and cushions the entire body," while relaxing muscles.

Sensuality: "The sensual swimmer knows how pleasurable it is to use one's muscles to move through the water."