Operator was driving a 1997 Crownline (IA registration 1686AM) near Fort Dodge Point on West Okoboji Lake.  A larger vessel crossed in front of the Crownline, causing a large wake ahead of the Crownline.  The Crownline broke through the first wake, slowed down and dropped approximately 5 feet before encountering the second wake.  When the Crownline hit the water, occupant who was sitting in the bow of the boat, injured her lower back when she landed back on her seat.  occupant leaned forward to brace herself for the drop from the wake and landed hard on her rear, where she felt instant pain in her lower back.  occupant was taken by ambulance to the Lakes Regional Hospital. She was not wearing a PFD.
OKOBOJI                       