Varying the routine with water walking or water jogging can perk up an otherwise repetitious pool workout. Water walking, which merely involves walking as fast as possible in water that is waist-high or chest-high, can burn more calories than water jogging, which is done in deep water.

"With water walking, you have some resistance because your feet are touching the bottom of the pool," said John R. Spannuth, executive director of the United States Water Fitness Assn. in Boynton Beach, Fla. Water walking can burn up to 460 calories an hour, compared to water jogging, which can burn about 400.