In a small bowl, beat sweetened condensed milk and water on medium speed until combined (about 1 minute).
Add pudding mix and beat for 2 more minutes.
Cover and refrigerate for 3–4 hours or overnight to set.
In a large bowl, whip heavy cream on medium speed until stiff peaks form.
Gently fold the pudding mixture into the whipped cream until smooth and streak-free.
In a large glass bowl (4–5 quarts), layer one-third of the wafers, bananas, and pudding.
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