Process graham crackers, mix with sugar, salt, butter: Pulse the graham crackers in a food processor or blender until finely ground. Put in a large bowl, and stir in the sugar and salt. Stir in the melted butter.
Preheat oven to 350°F (175°C), with rack in lower third of oven.
Press the graham cracker crumbs into the bottom of a 9 inch springform pan: Gently press down on the crumbs using your fingers, until the crumbs are a nice even layer at the bottom of the pan, with maybe just a slight rise along the inside edges of the pan.
Bake the crust: Place the pan on a baking sheet and bake at 350°F (175°C) for 10 minutes. Remove from the oven and let cool. While the crust is cooling, you can skip ahead and start on the filling. Wait until the crust has cooled to wrap the pan in foil in the next step.
Triple wrap pan in heavy duty foil: Prepare the springform pan so that no water leaks into it while cooking. Place a large 18-inch by 18-inch square of heavy duty aluminum foil on a flat surface.Place the springform pan in the middle of the foil. Gently fold up the sides of the foil around the pan. Make sure to do this gently so that you don't create any holes in the foil. Repeat this 2 more times so you have 3 layers of foil. You can also use a slow cooker liner.
Make the cheesecake filling: Beat cream cheese, then sugar: Cut the cream cheese into chunks and place in the bowl of an electric mixer, with the paddle attachment. Mix on medium speed for 4 minutes until smooth, soft and creamy. Add the sugar, beat for 4 minutes more.
Add salt, vanilla, then eggs, then sour cream: Add the salt and vanilla, beating after each addition. Add the eggs, one at a time, beating for one minute after each addition. Add the sour cream, beat until incorporated.
Add the heavy cream, beat until incorporated. Remember to scrape down the sides of the mixer bowl, and scrape up any thicker bits of cream cheese that have stuck to the bottom of the mixer that paddle attachment has failed to incorporate. Stir in your lime juice and zest.
Bake the cheesecake: Prepare pan and boiling water: Place the foil-wrapped springform pan in a large, high-sided roasting pan. Prepare 2 quarts of boiling water. Lower the heat on the oven to 325°F (160°C).
Pour filling into pan: Pour the cream cheese filling into the springform pan, over the graham cracker bottom layer. Smooth the top with a rubber spatula.
Place in oven: Place the roasting pan with the springform pan in it, in the oven, on the lower rack.
Carefully pour the hot water into the roasting pan (without touching the hot oven), to create a water bath for the cheesecake, pouring until the water reaches halfway up the side of the springform pan, about 1 1/4 inches. (Alternatively you can add the water before putting the pan in the oven, whichever is easier for you.) Bake at 325°F (160°C) for 1 1/2 hours.
Turn off the heat of the oven. Crack open the oven door 1-inch, and let the cake cool in the oven, as the oven cools, for another hour. This gentle cooling will help prevent the cheesecake surface from cracking.
Chill 4 hours: Cover the top of the cheesecake with foil, so that it doesn't actually touch the cheesecake. Chill in the refrigerator for a minimum of 4 hours, or overnight.
When ready to serve, remove the foil. Run a knife around the edges and remove the outer ring of the pan. Make the whipped topping: Pour the cream into a well-chilled bowl and add the sugar and vanilla. Using an electric hand mixer or balloon whisk, beat the cream to the desired consistency. For soft peaks, the cream will be just thick enough to hold its shape in soft billows. For stiffly beaten cream, the beaters or whisk wires will leave distinct traces on the cream and stand in firm peaks when the beaters are lifted. Spread the topping onto the cheesecake or serve on the side.