Swimming on the ball can be done. Place your stomach on the ball & roll the ball under your hips. Deepen the abdominals. Lift your legs off the ground and begin to flutter the legs. (20 Reps, counted 1-2-3 1, 1-2-3 2, etc.) Variation, do the same excersize crossing the feet at the ankle rapidly, wrapping. Be sure to keep the Abdominals engaged as well as the buttocks.

You may then wish to work your arms by continuing to roll the ball down to your knees and bending at the elbows, push-upsBe sure to engage the abdominals, keeping the body in a straight line. Deepening the Abs as you bend the elbows. Do not sag in the middle. If you find that you cannot help but sag rest for 40 sec and begin again, try to complete one last set with good form. (8 reps)