01 - Preheat oven to 350°F. Grease a 9x13-inch baking pan thoroughly.
02 - Combine the cake mix, water, oil, and eggs in a large bowl. Beat on medium speed for 2 minutes until completely smooth and well incorporated.
03 - Pour the batter into the prepared pan and bake for 28-32 minutes, or until a toothpick inserted in the center comes out clean.
04 - Remove the cake from the oven and allow it to cool in the pan for 15 minutes.
05 - Using the handle of a wooden spoon, poke holes all over the surface of the cake, spacing them approximately 1 inch apart.
06 - Dissolve the lime gelatin in boiling water, stirring until completely dissolved. Stir in the cold water.
07 - Slowly pour the gelatin mixture evenly over the cake, ensuring it fills the poke holes completely.
08 - Refrigerate the cake for at least 2 hours to allow the gelatin to set completely.
09 - Spread the whipped topping evenly over the entire surface of the chilled cake.
10 - Sprinkle with fresh lime zest and add green sprinkles or lime slices if desired. Cut into squares and serve chilled.