In a large mixing bowl, combine the sweetened condensed milk and ice cold water. Add the instant vanilla pudding mix and whisk until fully combined. Let the mixture sit for about 5 minutes to thicken.
In another bowl, whip the heavy cream until stiff peaks form. This might take a few minutes, but the result will be a fluffy, airy cream that will elevate your pudding.
Gently fold the whipped cream into the pudding mixture using a spatula. Be careful not to deflate the cream; you want to keep that light and fluffy texture.
In your baking dish, start by placing a layer of vanilla wafers at the bottom. Follow this with a layer of sliced bananas, then top with a generous portion of the pudding mixture. Repeat the layers until all ingredients are used, making sure to finish with the pudding on top.
Cover the dish with plastic wrap and refrigerate for at least 4 hours, or overnight if possible. This allows the flavors to meld beautifully and ensures that the wafers soften just right. Serve chilled and enjoy!