You can find this exercise on page 208 of the book Synergistic Golf.
Exercise Type: PRE-ROUND WARMUP
Exercise Category: ARMS - HANDS, CLUB CONTROL - ACCURACY, FLEXIBILITY
Stand with fingers interlaced together and palms open in front of chest. Flap arms like a wave keeping fingers interlocked. Keep rhythm going 5x one direction then reverse. Elbows will be out wider than shoulders. Perform loosely and without too much control.