In a small saucepan over medium heat, combine granulated sugar and water, stirring until the sugar dissolves completely. Allow to simmer for about 5-7 minutes, or until it turns golden brown. Carefully pour the hot caramel into a baking dish and set aside to cool.

In a large mixing bowl, whisk together the sweetened condensed milk, evaporated milk, whole milk, heavy cream, eggs, vanilla extract, and salt until smooth. Ensure no lumps remain.

Pour the custard mixture over the cooled caramel in the baking dish. Place in a larger baking pan filled with hot water halfway up the sides. Bake in a preheated oven at 350°F (175°C) for 50-60 minutes.

Allow to cool at room temperature for about 30 minutes. Then refrigerate for at least 4 hours, preferably overnight.

Run a knife around the edges of the flan to loosen it. Invert onto a plate, allowing caramel to cascade over the top. Garnish if desired and serve.