I don't know if this works, but if you crush moth balls and spread them around your dock or where you walk. It contains the stuff that is in snake away they sell at home depot. I go to the dollar store and buy it buy the case. Be careful when you crush, I put in a burlap sack and run over it with my truck. Like I said, don't know if it works, but it makes my wife feel safe. I think 99% of snakes seen in my lake are just water snakes, that no more want any part of you, then you of them.
Bob