Call a professional. Once you've identified the snake as a water moccasin and you've determined that you cannot keep the snake from making its way onto your property, call a professional exterminator that is skilled in dealing with snakes. Again, the water moccasin is a venomous snake whose bite can cause severe health problems in humans. While water moccasin's aren't typically aggressive, they will strike if they feel threatened or sense danger. If not treated properly and quickly, a water moccasin's bite can be deadly.