Whisk together the cold water and sweetened condensed milk in a medium-sized bowl. In a separate bowl, pour in the pudding mix and begin to slowly whisk in the liquid mixture, until it is smooth with no lumps, about one minute. 

Cover and refrigerate for at least an hour until it's firm, or leave overnight.

Whip the heavy cream until it starts to thicken, then increase the speed until stiff peaks form.

Add your pudding mixture to the whipped cream and fold with a spatula until there are no streaks of pudding in the mixture.

In a trifle or wide glass bowl, spread one-quarter of the pudding over the bottom and place a layer with one-third of the cookies as well as about 1 to 1 1⁄2 of the sliced bananas to cover the full layer. 

Continue the process until complete, ending with one final layer of pudding and a garnish of some of the remaining wafers. 

Cover the bowl with plastic wrap and refrigerate for four to six hours. It's recommended to serve the dessert within 12 hours. Just before serving, top with additional slices of fresh bananas.