UNIT 1 WAS TRAVELING NORTH ON THE WACCAMAW RIVER. UNIT 2 WAS TRAVELING SOUTH ON THE WACCAMAW RIVER. UNIT 1 FAILED TO MAINTAIN PROPER LOOK OUT AND COLLIDED HEAD ON WITH UNIT 2. UNIT 2 STATED THEY TRIED YELLING AND WAVING THEIR HANDS TO STOP UNIT 1 FROM HITTING THEM. UNIT 1'S OPERATOR WAS TRANSPORTED TO COMMUNITY HOSPITAL FOR MEDICAL TREATMENT.