In a large bowl, beat together the sweetened condensed milk and 1 ½ cups ice cold water until well combined - about 1 minute. Add the pudding mix and beat well - about 2 minutes. Cover and refrigerate for 3-4 hours or overnight.

In another large bowl, whip the 3 cups heavy cream until stiff peaks form. Gently fold the whipped cream into the pudding mixture until no streaks of pudding remain.

Dessert can either be made in individual portions or in a large glass bowl with 4-5 quart capacity (a 9x13 baking dish also works).

To assemble dessert, arrange ⅓ of the Nilla wafers covering the bottom, overlapping if necessary. Next, layer ⅓ of the bananas, and ⅓ of the pudding mixture. Repeat twice more, garnishing with additional wafers or wafer crumbs on the top layer. Cover tightly and allow to chill in the fridge for at least 4 hours - or up to 8 hours.