For the Ice Cream Base, Whisk together sweetened condensed milk, regular milk, key lime juice, and lime zest..
Place mixture in refrigerator for 30 minutes.
Next pour mixture into ice cream machine and churn according to machine's instructions.
While ice cream churns, puree mango, granulated sugar and water together until well blended and smooth.
In a separate bowl, mix together graham cracker crumbs, granulated sugar and melted butter until well combined.
Once ice cream is finished churning, alternately scoop ice cream base, then graham cracker crumbs, ice cream again and finally mango swirl into container until all ingredients are in the container.
Freeze for at least 4-5 hours and then serve.