Generously butter a 12×18 inch cookie sheet. Set aside.
Mix sugar, water, and corn syrup in a heavy skillet. Stir well until it comes to a boil. Cover and boil 3 minutes. Continue to boil to hard ball stage (when a little bit dropped into a cupful of cold water forms a hard ball – hence the name!) 250 degrees F (120 degrees C).
Stir in butter and peanuts. Continue cooking until mixture turns a light brown color. Remove from heat.
Mix together salt, vanilla, baking soda and water. Combine this with syrup and nuts mixture. Mix well, and fast.
Pour onto prepared cookie sheet. Use back of buttered spoon to spread thinly and evenly. Allow to cool, then break into pieces. Store in airtight container in refrigerator.