Operator and three witnesses pulled up and stopped to look at the water fall. According to eighteen year old witness, victim started shaking "like he was having a seizure" and fell overboard. He made no attempt to swim. The victim was not wearing a PFD. Witness stated that victim had 3-4 beers earlier in the day. Completed report is pending the toxicology report. Medical examiner reported that the combination of pain medication and alcohol could cause seizure like symptoms.