In a medium mixing bowl, whisk together the sweetened condensed milk and ice-cold water until well combined. Add the instant vanilla pudding mix and whisk for about 2 minutes until smooth. Cover the bowl and refrigerate for at least 4 hours or overnight, until the mixture is firm.

In a large mixing bowl, use an electric mixer to whip the heavy cream on medium-high speed until stiff peaks form. This should take about 3-4 minutes.

Gently fold the whipped cream into the chilled pudding mixture in three additions, being careful not to deflate the whipped cream. Continue folding until no streaks remain and the mixture is smooth and fluffy.

In a trifle dish, begin layering the dessert. Start with a layer of vanilla wafers, followed by a layer of sliced bananas, and then a layer of the pudding mixture. Spread the pudding evenly to cover the bananas and wafers.

Repeat the layers (wafers, bananas, pudding) until all the ingredients are used, finishing with a layer of pudding on top. Reserve a few wafers for garnish, if desired.

Cover the trifle dish tightly with plastic wrap and refrigerate for at least 30 minutes to an hour, or until the wafers have softened and the flavors have melded together.

Before serving, garnish the top with the reserved wafers or additional banana slices, if desired. Enjoy!