Combine sugar, corn syrup and water in heavy skillet. Cook slowly; stir until sugar dissolves. Cook to soft ball stage. Remove the candy from heat while testing. Add nuts and salt to mixture. Cook to hard crack stage, stir constantly. Remove from heat. Add butter and baking soda and stir to blend. Mixture will bubble. Pour onto greased platters. Cool partially by lifting around edges with spatula. Keep spatula moving under mixture so it won't stick. When firm but warm, Turn over. Break in pieces when cold.