Preheat the oven and prepare the white cake batter following the instructions on the box. Transfer the batter into a greased 9x13-inch pan and bake until a toothpick inserted into the center emerges clean. Once baked, allow the cake to rest and cool slightly for 10 to 15 minutes.
Once the cake has cooled a bit, use the handle of a wooden spoon to pierce evenly spaced holes across the surface of the cake.
In a medium bowl, stir the raspberry gelatin into the boiling water until fully dissolved. Blend in the cold water. Gently pour the gelatin mixture across the cake, allowing it to seep into the holes.
Warm the raspberry preserves in the microwave for 20 to 30 seconds until fluid but not hot. Evenly distribute the melted jam over the top of the cake. Refrigerate the cake for a minimum of 2 hours, or until completely chilled.
After the cake is well-cooled, evenly spread the thawed whipped topping across the surface. Scatter the sweetened coconut generously over the whipped layer.
If desired, top with fresh raspberries for an added touch of color and flavor.
Slice the finished dessert into squares and serve chilled.