Lay out several sheets of foil to spoon the hot peanut brittle onto.
In a large skillet mix the sugar, syrup, and water together. Cook at a medium-high heat, stirring regularly. Heat until the mixture has a hard ball consistency. Heat to 250 to 265 degrees F (121 to 129 degrees C), or until a small amount of syrup dropped into cold water forms a rigid ball. If you don't own a candy thermometer, occasionally hold spoon above mixture, allowing it to drip off spoon. When mixture is at hard ball stage, it will 'hair' off the spoon when falling, looking like a clear spider web.
Once mixture is at hard ball consistency, add raw peanuts. (They will pop a little.) When mixture starts to turn a light clear-brown, as if it's starting to burn, remove from stove. Add soda and stir. Mixture will foam up.
Spoon out bite-size pieces onto unbuttered foil, stirring constantly between each couple of pieces. Mixture can also be poured onto unbuttered foil as one big piece and broken into smaller pieces once cooled.