Could have done but i don't know, fully getting in the water and getting all his clothes wet and cold just to wash off some blood? Why not take the phone from the car to call someone for help? Also even thought he may have done seems odd that he'd go to the water if he felt faint, you would think sitting on the car and calling someone on the phone would be his number one priority, also the car was found still running so i imagine the accident may not have been so bad as to make him go unconcious shortly after, maybe a concusion but then it would make more sense that he felt sleep in the car and died there, but instead he managed to go all the way to the water, and i doubt he went to sleep there. Maybe the car crashed because he struggled with someone in the car and this unknown person drowned him.But the information about how he was found is quite vage, so we don't know if someone was there, and why he went there that day, and other details that we need.