While traveling south on the icw unit 1 hit a walkway connecting dock. The dock was located off of goat island across from the isle of palms. Throughout the day two people were captains of the vessel. however, original statements put subject1 as the operator at the time of the accident. At approximately 2200 hours the vessel left the morgan creek area with subject2 as the captain. After a small boat passed them headed north of the icw he operator was changed to subject1 being that he had local knowledge of the area and was more familiar with the boat operation. It is noted the distance between the closest dock north and the hit dock is approximately 800 yards on the goat island side of the icw. Injuries: victim2 cut to the right side of head/ear. Victim3 head injury, ribs, and c2 fracture. Victim1 head injury, right arm, and right ear.