In a heavy-bottom saucepan, combine the water and sugar. Make sure the sugar is submerged in the water. Over medium heat, stir constantly with a rubber spatula or wooden spoon until the sugar is dissolved and the mixture begins to bubble. Make sure you use a slightly bigger saucepan than what you think you may need. Increase to a medium-high and leave it alone. Don't stir at this point at all. Make sure during this period, you brush the sides with water to ensure the sugar doesn't crystallize. Let the mixture boil until it reaches a nice golden brownish color. The darker the bubbles, the darker your end caramel will be. The lighter they are, the lighter your caramel will be.  Once the proper color is achieved, remove from the heat and whisk in the heavy cream slowly. It will bubble up. That's normal. Just go slow and you'll be fine. Add in the butter in pieces and whisk in until fully incorporated. Whisk in the salt and then the vanilla. Pour the caramel sauce into a separate container to cool. It will thicken as it cools. Once cool enough, place in your squeeze bottle or plastic container to store. Store in the fridge for up to two weeks.