There are more ways to exercise in a swimming pool than just swimming laps. There’s water aerobics and synchronized swimming, and then there’s deep water running. Deep water running is low impact—and therefore easy on the joints—and a growing favorite among those who are recovering from stress fractures, muscle tears, or other conditions that prevent them from running on land, or those who are looking to expand their exercise options.
To go for a deep water run, you will need a bathing suit well, I guess that depends on where you're swimming..., a flotation vest or belt, and water at least a few feet deeper than you are tall. The idea is to keep yourself in an upright position, head facing forward, body tilted slightly forward, while you mimic the motions of running on land: legs pumping, abs tight, hands clenched into loose fists. The deep water runner can be tethered in place (to increase resistance or to facilitate monitoring by a coach, therapist, or physician), or may actually run laps in the deep end of the pool.
Studies have indicated that deep water running “more closely simulates actual running than other forms of exercise”*, and it provides a viable cross training option for people who cannot run or prefer a more low impact form of aerobic exercise. The body’s buoyancy when in water means a greater range of motion is possible; additionally, water provides more resistance to movement than air, so the swimmer receives both a cardiovascular and strength training workout. Additional resistance can be created using aqua “socks” or gloves, or specially designed dumbbells.
You don’t have to wear a flotation belt while deep water running, but if you do, it is easier to maintain the proper posture in the water and focus on maintaining good form and increasing your heart rate, rather than on staying upright and afloat.
I have taken classes that consisted of nothing but timed sprints followed by recovery jogs, but there are a wide variety of other motions that can be performed which are aerobically beneficial (and more entertaining than sixty minutes worth of running back and forth across the deep end.) These include intervals of cross country skiing, “wide” jogs, hurdles (in which the swimmer performs a breaststroke move with the arms, while ‘leaping’ forward with first one leg, then the other), and flutter kicks, which are performed with the swimmers’ hands out of the water, above their heads. Classes are usually 45 minutes to an hour long, are set to music, and include warm-up and cool-down periods. Afterwards, we all sink happily into the nearby jacuzzi.
* http://sportsmedicine.about.com/gi/dynamic/offsite.htm?site=http://hsc.virginia.edu/medicine/clinical/phys-med-rehab/obser100.html
http://www.adventuresportsonline.com/deepwater-run.htm
http://sportsmedicine.about.com/library/weekly/aa032002a.htm