In a large bowl, whisk together the pudding mix, sweetened condensed milk, and cold water until smooth. Refrigerate for 10 minutes to thicken.
Whip the heavy cream in a separate bowl until soft peaks form.
Gently fold the whipped cream into the pudding mixture until fully incorporated and smooth.
Slice bananas into 1/4-inch pieces.
In a trifle dish or glass bowl, layer vanilla wafers, sliced bananas, and pudding mixture. Repeat layers until the dish is full, ending with a layer of pudding.
Cover and refrigerate for at least 4 hours or overnight to allow the flavors to meld and the wafers to soften.
