You can find this exercise on page 271 of the book Synergistic Golf.
Exercise Type: PILATES
Exercise Category: BACK, HIPS, LOW BACK, RHYTHM - TIMING, STRENGTH
Lie face down with arms and legs outstretched hip and shoulder width apart. Inhale to prepare. As you exhale, maintain your back and pelvis in place while reaching your arms and legs slightly off floor. Inhale 5 counts while swimming arms and legs straight up and down in flutters. Then exhale 5 counts performing the same move. Continue the reciprocal swim action through 5 sets of inhales and exhales. Relax.