RedactedNarrative: Operator of Vessel 1 was attempting to throw anchor over cross beam approx 3' tall under bridge and fell in.  Operator was trying to use the anchor rope to stay afloat and pulled anchor onto his head. Operator told passengers he could not breath and passengers threw him his life jacket. Operator was able to make it to the bow of the boat and lost the life jacket and began to hold on to bow of boat. Operator was being hit by 3'5" waves and stated again that he could not breath. One of the passengers tried to give him a rope  but said he would not take it.  After a few minutes the victim was overtaken by waves and became partially submerged approximately 3 feet under the water. The accident occurred on Keystone Lake beneath the Highway US 412 bridge approximately 12' south of north pillar and 30' east of west bank.