Warm up with five to 10 minutes of moderate aquatic activity before performing abdominal exercises. Examples of water activities include swimming laps, water walking, water jogging and kickboard drills. Start slow as you acclimate to the water. Gradually increase your pace and intensity as you move through the warmup session.
Perform a traditional pike exercise in the pool to target your rectus abdominis. Stand in a level of water where your feet are firmly on the bottom of the pool and your head is completely out of the water. Pull your abdominal muscles in toward your spine and slightly tuck your tailbone down. Tread water with your hands at your sides as you lift your toes out of the water in front of you until your body forms a wide V-shape. Maintain a straight torso, slightly lift your chest and push your shoulder blades down and away from your ears. Cup your hands and make small circle movements to propel yourself forward for 30 seconds. Release by lowering your feet and returning to standing position. Repeat for a total of three repetitions.
Use a pool noodle to perform tucks. The noodle helps to keep your head and shoulders above water level during the exercise. Place the pool noodle around your upper back and hold the ends in front of you. Extend your legs straight in front of you, toes pointed. Engage your rectus abdominis and bring your knees in, tucking them to your chest. Hold the contraction for two counts. Extend legs back out in front of you and repeat for up to five minutes or until you have reached fatigue, which means that you cannot perform another repetition with proper form.
Move to an area of the pool where you cannot touch the bottom to perform the k-tread exercise. Begin treading water, making circle motions with your hands. Extend your right leg straight in front of you while pointing the left toes toward the bottom of the pool. Your body should be in the shape of a K. Continue to tread water with your body in this position for five seconds before alternating legs quickly and holding for another five seconds. Continue alternating the leg positions for 30 seconds or until fatigued.