RedactedNarrative: Vessel 1 followed Vessel 2 on the Wisconsin River Upper Dells downriver to the southeast from the Birchcliff Beach.  When both boats were near the middle of the river channel, just south of High Rock, Vessel 2 turned sharply around in the water and faced toward the direction of Vessel 1.  Vessel 1 collided with Vessel 2 causing the operator of Vessel 2 to suffer a broken femur.  Both operators were ejected into the water.