In a medium bowl, mix graham cracker crumbs, sugar, and melted butter until well combined. Press firmly into the bottom of a 9-inch springform pan and refrigerate for at least 30 minutes.

In a small bowl, sprinkle gelatin over cold water and let bloom for about 5 minutes. Heat in the microwave for 10-15 seconds until dissolved and set aside to cool.

In a large mixing bowl, beat softened cream cheese with powdered sugar until creamy, gradually adding lime juice, lime zest, and vanilla extract until fully incorporated.

Whip heavy cream in a chilled bowl until stiff peaks form, being careful not to over-whip. Set aside.

Drizzle cooled gelatin into the cream cheese mixture while mixing on low speed. Fold in the whipped cream gently until smooth and airy.

Pour the lime mousse filling over the crust in the springform pan, smoothing the top. Cover with plastic wrap and refrigerate for at least 4 hours or overnight.

Once set, remove from the fridge and release the springform pan. Optionally, garnish with lime slices or zest and serve chilled.